Opposite Gender Protagonists

"A young boy and a girl with a magic crystal must race against pirates and foreign agents in a search for a legendary floating castle."

- Laputa: Castle in the Sky summary on IMDB

A strong way to create an emotionally resonant and impactful relationship is having The Heroes of the story be opposite genders. In other words, the main characters are a boy and a girl. The two go on adventures, help each other get out of sticky situations, experience The Power of Friendship, and sometimes fall in love. This trope is quite unpredictable, but what's almost guaranteed is that the two stick together through the story. There may be a Second Act Breakup, but you can rest assured that they'll eventually get back together.

Remember this is a character driven trope, based heavily on how characters come together. In order for something to quality:
 * 1) The leads must be protagonists. If the male lead is the protagonist, then the female cannot be a mentor, parent, or any other character who doesn't play a central role. Check if the characters' ages are the same. If they are, then it almost always fits. If it doesn't, then there's a chance it may not; proceed with caution.
 * 2) There should be two characters clearly identifiable as the protagonists. A Ragtag Band of Misfits does not count. Similarly, a trio of two girls and one boy or two boys and a girl is also disqualified.

Generally speaking, this is used more in Film than in TV shows. In a movie, you've only got two hours to introduce and develop not only the characters, but the whole world, story, and make them come together in a satisfying way. The amount of characters you can have before other aspects are compromised is much lower. Spend too long on crafting characters, and the story will come to a standstill. Having only two central characters means their relationships can be well-developed without interfering with storytelling. It's common for long-running shows or books to start out using the trope. Then, as the series progresses and more characters are introduced, no single character can be defined as a protagonist as their roles are delegated to a larger group, therefore ending the trope's usage.

Battle Couple is related, where there is an explicit romance between the leads. A Battle Couple may be of the same sex (Ho Yay!), but Opposite Gender Protagonists cannot. Furthermore, a Battle Couple must see battle, whereas people in Opposite Gender Protagonists don't. A Slice of Life story does not work with a Battle Couple, but is made more powerful using Opposite Gender Protagonists. These characters may be a Brother-Sister Team. A typical combination is The Hero with their Love Interest.

Contrast Heterosexual Life Partners, Platonic Life Partners — where the couple don't have to be the main characters and they are not dating — Two Guys and a Girl, and Two Girls and a Guy. If the trope is used, then expect some variation on Boy Meets Girl.

Anime and Manga

 * Happens frequently in Studio Ghibli productions, where the female lead is always a Plucky Girl:
 * Asbel and the titular Nausicaä in Nausicaä of the Valley of the Wind, predating the studio. Nausicaä is easily the main character, playing a much bigger role than Asbel. Asbel only has a major role in the second act. Still, that doesn't stop them from sharing sweet scenes and helping each out when they land in the deadly Sea of Decay.
 * Sheeta and Pazu from Laputa: Castle in the Sky, who is almost the textbook example of this trope. The two go on adventures, face many difficulties, and are even separated at one point, before uniting with each other. In other words, it's a typical Boy Meets Girl plot. Being children racing against the military and finding a Castle in the Sky is difficult, and them being the protagonists strengthens their relationship.
 * Kiki and Tombo in Kiki's Delivery Service, who start out disliking each other. Kiki believes it's rude to talk to a girl before you've been introduced to her, leading to her attitude towards Tombo. Once Kiki saw who Tombo really was, she started to open up to him. Tombo has a passion for aviation, making Kiki a perfect friend, as her witch powers enable her to fly. The ending sequence shows them flying together; Tombo on the plane he built, and Kiki on her broomstick. The two protagonists, despite having great chemistry, never engage in romance, instead being Implied Love Interests and the work remains No Hugging, No Kissing.
 * Fio and Porco from Porco Rosso. Porco is a Ace Pilot, and Fio a brilliant engineer. Fio jumps on Porco's plane to ensure he'll pay his debt back and to assist him with his newly modified plane. Fio's hand in marriage is used in a wager at the end of the film. Their interactions and Fio's Plucky Girl attitude provides humorous interactions. Porco barely wins the wager, and sends Fio away with Gina. The two leads do not engage in a romance, and Porco chooses Gina to be with at the end.
 * Seiji and Shizuku in Whisper of the Heart, where the relationship is developed into a romance. The two start out bickering, with Shizuku disliking Seiji as he mocked her lyrics for the Real Song Theme Tune "Country Roads". Later, while singing and playing music at night, they get over their differences and start forging a relationship. Shizuku, believing that she is lacking in talent and is lost for what to do in life, looks up to Seiji, a violin maker. She eventually picks up writing, and writes the titular Whisper of the Heart Story Within a Story. This relationship gives audiences a reason to care when Seiji eventually departs to Italy, as well as allows them to understand the significance of the moment when Seiji returns.
 * Ashitaka and San in Princess Mononoke. Ashitaka, after being cursed, journeys to the west and finds an epic conflict involving Iron Town, led by Lady Eboshi, and the inhabitants of the forest, one of which is San. The pair learns to work together, and eventually saves Iron Town and its inhabitants. Ashitaka never takes sides, so he never joins anyone in the war. This eventually leads to a romance, which they cannot pursue because of San's hatred for humanity. At the end of the film, San lives in the forest, while Ashitaka lives in Iron Town, although the two do occasionally visit each other.
 * Haku and Chihiro in Spirited Away. Haku helps Chihiro navigate the perils of the spirit world, and helps her get a job, find her parents, and avoid being turned into a pig. In return, Chihiro helps Haku remember his true name, and to help him move on from being Yubaba's apprentice. A romance between the two ensues, resulting in a Free Fall Romance when Chihiro informs Haku about his true name as the two start Holding Hands. All of this makes the film emotional when the two inevitably have to say goodbye at the end.
 * The Baron and Haru in The Cat Returns. Them being two completely different species does not stop a bond forging between them. Haru seeks the Baron for help after being blessed with gifts she does not want. All she did was save a cat from a truck! She does not need to marry this crazy Cat King's son. Knowing she will be dragged off to the Cat Kingdom, she talks to the Baron and asks for help. When Haru is inevitably taken to the Cat Kingdom, the Baron leads Haru back to the human realm. After the adventure, Haru even admits that she has a little crush on the Baron.
 * Aaron and Therru in Tales From Earthsea. There are less character dynamics, due to the relative inexperience of director Goro Miyazaki, than in other Ghibli productions. The two aren't together for long stretches of the runtime, only reuniting in a Deus Ex Machina at the end.
 * Ponyo and Sousuke in Ponyo on the Cliff by the Sea. The characters are both around five years old, but that doesn't stop the trope from being used for romance. Ponyo, after tasting Sousuke's blood, wishes to become human. Once the "boy loses girl" and "boy finds girl" part of Boy Meets Girl happens, the two get The Glomp and play in Sousuke's house. After a massive flood caused by Ponyo's departure, throwing off the world's balance, Sousuke's mum Lisa departs to look after elderly residents, leaving the two alone for the night. When she didn't return the next morning, the two set out to search for them. The film focuses on the two navigating the environment, as well as the journey of Ponyo becoming human.
 * Howl and Sophie from Howl's Moving Castle, also occurring in the novel of the same name. Here, the trope is used as a vessel for a romance, as the two leads meet and slowly fall in love. It gives Howl something to protect, and Sophie something to support her status as a newly cursed ninety-year-old woman. Howl builds a garden for Sophie, after finding something he wants to protect.
 * Arrietty and Sho in The Borrower Arrietty. Arrietty is a member of a race of Lilliputians called the Borrowers who take things from humans they won't miss. Sho is a human with heart problems, needing a quiet, secluded environment to live in. The Huge Guy, Tiny Girl dynamic between the two, as well as the fact that Arrietty isn't allowed to visit the boy -- human beings are perceived as dangerous by Borrowers -- make this pairing stand out. The two are dependent on each other: Sho needs someone to support him with his heart condition; and Arrietty is powerless due to her small size, and needs help from a human to navigate the confusing world. Thus, placing them at the center of the film strengthens their relationship, and gives audiences a feeling of sorrow when they inevitably have to part.
 * Umi and Shun in From Up on Poppy Hill. The two work together to save the Quartier Latin clubhouse. The clubhouse is set to be demolished, making way for a new generation and moving on from the past, giving them something to work towards. They take a trip to Tokyo to convince the head of the school board to let it stay. Umi is called the "Goddess of Good Luck" by other students, so her and Shun make a powerful combination while doing this. These events are backdropped by a romance blooming between the two characters, adding intrigue to their character dynamics.
 * Nohoko and Jiro in The Wind Rises. Jiro meets Nohoko during the Great Kanto Earthquake, and helps her and her family. Several years later, the two fall in love, being Star-Crossed Lovers. This trope is used to develop their relationship, and create sweet romance scenes.
 * Sutemaru and the titular Princess Kaguya in The Tale of the Princess Kaguya. Sutemaru does a Diving Save to save Princess Kaguya from a charging boar and calls her "Little Bamboo" to reflect how quickly she grows up. A major plot point revolves around Princess Kaguya trying to return to the Arcadia lifestyle she and Sutemaru lived before being forced to move into the capital. Their relationship provides something special for Princess Kaguya to return to. Sutemaru is established to be helpful, kind, and most importantly genuine, whereas members of royalty are established to be fake, and contrived, wishing only to marry Princess Kaguya for her beauty instead of who she really is.
 * The unnamed man and titular red turtle in The Red Turtle. The man is washed up on the deserted island the turtle resides in. The turtle, wishing for companionship, prevents the man from leaving, destroying his bamboo raft when he tries to get out. Insistent on leaving the island, the man flips over the turtle and leaves her beached. After Humanity Ensues with the turtle, the man starts looking after the turtle — well, girl — and becomes genuinely nice towards her. They even have kids, and survive on the island as a family, growing old.
 * Mary and Peter in Mary and the Witch's Flower. Considering that the production studio Studio Ponoc descended from Ghibli, there are no surprises here. The trope is used to establish and strengthen the relationship between the two lead characters, and later give Mary a reason to return to the Wizarding School.
 * Maquia: When the Promised Flower Blooms stars Maquia and Erial. This is an interesting case, due to their age difference. It's clear that Maquia is the protagonist, however Erial, being the orphaned child, plays a huge role in the film, as the film focuses on his growing up and interactions with his mother Maquia, who does not age and is stuck looking eternally young. Instead of the heroes facing an external conflict, the first part of the film sees the heroes facing an internal conflict between themselves, before introducing an external source of conflict with a war.
 * In Your Name, Taki Tachibana and Mitsuha Miyamizu.

Comic Books

 * Shuna's Journey--illustrated by Hayao Miyazaki from the long list of Studio Ghibli examples in the Anime and Manga section--features Shuna and Thea. Shuna rescues Thea from slavery. Thea repays the favour by nourishing Shuna back to health later on, because Shuna was nice to her. The two briefly interact, and don't exchange many lines, but their relationship has a huge impact on each other.

Film

 * Buttercup and Westley in The Princess Bride. The two leads instantly fall in love in the first three minutes of the movie, and Westley's departure makes Buttercup worry about when he will return. Buttercup is put into an Arranged Marriage as Westley never returned and gets kidnapped, starting the conflict. Eventually, the two meet up again, and they help each other through their adventures, bringing them closer together, leading up to a Big Damn Kiss.
 * Tristan and Yvaine in Stardust, where the trope is used again as a vessel for romance. Tristan initially sees Yvaine, a falling star turned girl, as a present for his lover Victoria, but he falls in love with Yvaine during their trip back to his hometown. Yvaine comments that, as a star, the violence and wars on Earth make her exhausted, but love gives her faith in the planet, developing the relationship between the two leads. This leads to Tristan rescuing Yvaine after she's kidnapped in the climax.
 * Hiccup and Astrid in How to Train Your Dragon. Hiccup starts with a crush on Astrid, but his clumsy nature contrasts with Astrid's skills as a fierce warrior, leading to a gap between the two leads. The gap grows smaller and smaller as Hiccup finds and tames Toothless, a feared Night Fury. Astrid starts to see Hiccup's ways with dragons, and over the course of the trilogy they grow closer. This results in their marriage at the end of How to Train Your Dragon: The Hidden World.
 * Pixar productions:
 * Marlin and Dory in Finding Nemo. The main character is Nemo, however the two characters play just as important, if not more important, of a role than Nemo himself. After Nemo gets taken away to an Australian dentist office, and displayed inside a container, it is up to the duo to find and save him.
 * Joe and 22 in Soul. The former is trying to get back into the human world from the spirit world. The latter is being forced to get into the human world and doesn't want to. Needless to say, this is a catch-22 situation which will force someone to have character development to get what they want. Joe, as a result of these interactions, learns messages about how to live in life.
 * WALL-E and EVE in WALL-E, where the romance delivered by the trope is as strong despite the leads being robots. WALL-E, living on a deserted, trashed Earth for several hundred years, is more than happy to have some sort of companionship in the form of EVE. When EVE is shut down remotely, and taken away, WALL-E follows, where the little guy attaches to a spaceship and goes to the Axiom, living with the rest of humans on the ship. It's a testament to how far the trope can be pushed and its applicability, as well as to Pixar's storytelling ability.
 * In Dragonslayer, Galen and Valerian. Valerian initially disguises herself as a man, but when it is revealed she is a girl, the trope comes into play. The trope is used to help deliver a romance between the two leads.
 * Joe and Rita in Idiocracy, where these two average citizens contrast the rest of the, well, "society". Being cryogenically frozen and forgotten, these two wake up 500 years into the future, with society around them crumbling to bits as the dumbest people reproduce the most. The smart people, on the other hand, wait for a good opportunity, an opportunity which may never come, before having a child. Joe is arrested for refusing to get a barcode tattoo, whereas Rita is wanted by almost every single male as a hooker. The pairing provides some semblance of sanity in a world where the most popular show is called Ow My Balls!
 * Valerian and Laureline in Valerian and the City of a Thousand Planets. Valerian constantly chases after Laureline, trying to get a Relationship Upgrade, and often breaks professional codes of conduct they're expected to follow. The two are assigned on a mission to the city of Alpha, where the duo must reach the center of the city, inside a radio dead zone. Cue character interactions as they try to get each out of sticky situations and understand strange alien customs.
 * Disney Animated Canon films. The trope is more commonly used in older productions, due to old Disney's usage of the Princess Classic. Also quite prominent in Disney renaissance films due to the studio returning to their roots:
 * Beauty and The Beast. Just because Belle and the Beast are entirely different species, with one of them being cursed, does not mean they cannot form a romantic relationship. The trope is used to enhance the 'fairy tale' feel of the film.
 * Jasmine and the titular Aladdin in the 1992 Aladdin film. This time, Jasmine is a Rebellious Princess, and her interactions with the titular Aladdin, as well as Aladdin's quest to make her fall in love, make up half of the film. The other half revolves around Aladdin's interactions with the genie.
 * Flynn and Rapunzel in Tangled. Just like the original fairy tale, the titular Rapunzel is locked away in a tower. Flynn, while running away from city guards, comes across the tower and climbs up. The two initially do not get along, with Rapunzel using her Rapunzel Hair to tie him to a chair and begin the world's most informal interrogation sequence. Eventually the two learn to get along, with Flynn convincing Rapunzel to move out of the tower, and explore the wider world, eventually leading the two to fall in love.
 * In Zootopia, Judy Hopps and Nick Wilde. They're opposites in more than gender -- one's a cop and the other's a con man, and in a World of Funny Animals, one's a prey and one's a predator.  The latter leads to interesting character interactions between the two as civil unrest grows between prey and predators.
 * In Atlantis: The Lost Empire, we have Milo Thatch, who joins an expedition to find the titular Atlantis. The second lead, Kida, isn't introduced until the party arrive at Atlantis. From there, Milo and Kida have some calm, Action Film, Quiet Drama Scene bonding sessions, before teaming up to save Atlantis from a greater threat.
 * Ralph and Vanellope in Wreck-It Ralph. One's the villain of a video game, and the other a playable hero. Being the Big Bad of a game doesn't feel good, and leads to Ralph being treated badly by the citizens in his own game. Thus, he defects, or "goes Turbo", from his own game, and found Vanellope in Sugar Rush, where the two bond together as Vanellope tries to use her status of being a "glitch" to her advantage.
 * Meg and Hercules in Hercules, where Meg serves to motivate the titular character. She often gets kidnapped, requiring Hercules to save her, advancing the plot. The two initially start out disliking each other, but slowly warm up over the course of the runtime. She is used by Hades as a bargaining tool, knowing that Herules will come to her rescue at some point.
 * In Disney's Moana, we have the titular Moana and Maui. This pairing is characterized by their interactions between one person trying to save the world and one retired hero who wants to relax and have fun. They are possibly the two least qualified people in the world to save the world. Bonus points for the alliterative names.
 * Dr Ryan Stone and Matt Kowalski in Gravity. There, they're forced to have good relationships and chemistry, because they're stuck up in space by themselves and everyone can see their faces. The Russians shot down a satellite, and, since they forgot about the Kessler syndrome, the debris from the satellite is quickly rushing towards them and threatening their survival. Thus, the two have to help each other make it back to Earth.
 * In the 2018 Mortal Engines film, Hester Shaw and Tom Natsworthy demonstrate many classical aspects of the trope: Boy Meets Girl, the two going on adventure, and the two saving each other from danger. The one missing element is romance.

Literature

 * Howl's Castle series:
 * Sophie Hatter and Howl from Howl's Moving Castle. Unlike the film, the two in the book are less friendly towards each other, with more bickering and arguing. Sophie, after being cursed, becomes a cleaning lady in Howl's castle. Howl is a peculiar man, living in a Trash of the Titans house, and refuses to let Sophie clean some areas, insisting that the spiders on the roof be kept alive. He constantly keeps calling Sophie "Mrs Nose". Eventually, they overcome their differences for the climax, and unite against the Witch of the Waste. Somehow, the two become lovers despite being the last two people you would pair together.
 * Charmain Baker and Peter in House of Many Ways. Charmain, sent to look after Great-Uncle William Norland's house, encounters Peter. Peter asks to be apprenticed to Wizard Norland, but arrives in the house while he's sick, when Charmain was in charge. The two do not get along, and their interactions provide some humour. Charmain, being a secluded child lacking many basic skills, has to learn from Peter how to wash dishes and hang up the laundry. Charmain only wishes to be a Bookworm, reading books instead of helping Peter out. She volunteers to sort out letters and books in the royal library, leaving Peter alone to do jobs in the house -- a fact which he complains about.
 * Flower-in-the-Night (yes, that's her name) and Abdullah in Castle in the Air. Abdullah, a carpet merchant, daydreams that he will be engaged to a beautiful princess. When he is sold a flying carpet, that dream comes true as the carpet takes him away to Flower-in-the-Night. Of course, things are never that simple, and after brief interactions she is taken away by a djinn to a Castle in the Sky; it's up to Abdullah to rescue her. In this case, the trope is used to motivate the male lead.
 * The unnamed boy and the Lilliputian Arrietty in The Borrowers. Arrietty reads to the illiterate boy, strengthening the bond between them. The boy, being far larger than Arrietty, protects her from the dangers the humans present.
 * Morrigan and her best friend Hawthorne in the Nevermoor series. In the first book, Hawthorne is notable for being the first person her age to become her friend. Back in her home town of Jackalfax, she is perceived as being a cursed child and blamed for all the misfortunes occurring around her. She and Hawthorne trial together for a position in the Wunderous Society, and in the second book plays a huge role in shutting down the Ghastly Market As the series progresses, the trope is used less as the rest of Unit 919 opens up to her and play a bigger role in the story, meaning there is no character clearly identifiable as a sidekick.
 * In George Orwell's Nineteen Eighty-Four, we have Winston and Julia. The two are lovers in an era where romance is strictly forbidden. Romance gives people a reason to step out of line, and to not obey and blindly consume everything the party says. This, combined with how Winston is already married, means the two have to hide their love in public, and find secluded places in private. In part III, we are shown the ruthlessness of the party in the Ministry of Love as the two are broken, betray each other, and lose their feelings. When they meet after being tortured and released, they feel nothing towards each other, and stare and talk without passion.
 * Tessa and Chuck in John Gordon's The Quelling Eye. They become friends early in the book and their relationship is cemented by their experiences. There is clear romance potential in the way they come to see each other but they remain only friends by the end of the book, likely because of their age.

Live-Action TV

 * Scarecrow and Mrs. King - right there in the title.
 * The X-Files, conspiracy-minded Agent Fox Mulder and skeptical Agent Dana Scully.

Music

 * Eurtan (katethegreat19)'s album Raindancer features "The Willow Maid", which tells the story of a man trying to take the titular willow maid in the forest, and make her his wife. The maid says no, but the man doesn't give up. The man eventually resorts to brute force, cutting down the maid's tree and forcing her to follow him. Needless to say, this does not end well, and the maid collapses, providing a rare case where the protagonists are working against each other.

Video Games

 * Dr. Eva Rosalene and Dr. Neil Watts in To the Moon, returning in the sequel Finding Paradise. They are two professionals travelling around to fulfil their clients' wishes before they die, and their interactions provide plenty of snarky responses, hilarious dialogue, and fun moments, contrasting with the emotional stories of the clients they help such as Johnny.
 * Within Johnny's story, he and River also qualify for this trope, as the two support each other throughout their lives and fall in love.
 * Raymond Lawrence and Laeticia Aucerius, the main male and female hero of Star Ocean 6. You can pick one as the canon main character, which will cause the story to focus more on events from their point of view whenever there is a story fork where they must split up. Certain characters can only be recruited for each one on their respective player path, and certain scenes are only viewable for each character. This means it's worth playing as each character once per playthrough to see all the content glossed over or not available when playing as the other.

Western Animation

 * The Pine siblings Dipper and Mabel in Gravity Falls, where they go on wacky hijinks around the town they stayed in for the summer.
 * Sprig and Anne in Amphibia. The fact that the former is a frog and the latter a thirteen-year-old girl does not stop them from going on whimsical adventures and yelling "Spranne against the world!" The trope is prominent in the first season, which mostly features lighthearted adventures in the frog world, although Sprig's family occasionally takes centre stage. Later, when the ice around Wartwood melts and Cerebus Syndrome kicks in, more human characters appear, and the trope is used less. In season three, emphasis is placed on both Anne and Sprig's family interacting, completely averting the trope's usage.