Opposite Gender Protagonists

One of the best ways to create an emotionally resonant relationship is having The Heroes of the story be opposite genders, and focusing on their interactions. In other words, the main characters are a boy and a girl. The two go on adventures, help each other out, experience The Power of Friendship, and sometimes fall in love. 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.

This is a great way to establish and forge a relationship between two characters. No one is perfect, but someone else can remedy our flaws, and make our best parts shine. Having Opposite Gender Heroes is a great way to establish a strong friendship, potentially developing into a romantic pairing. A couple that's been through a lot together, at the centre of the adventure, inevitably forges a stronger relationship.

This is useful for getting audiences invested within a work. Male demographics can sympathise with the male character, and female audiences see themselves in the other hero. When you appeal to both genders, expect to see your Ratings go up.

In order for something to quality:
 * 1) The male and female must be protagonists. If the male is the protagonist, then the female cannot be a mentor, parent, or any other character who doesn't play a central role.
 * 2) There should be two characters clearly identifiable as the main characters. A Ragtag Band of Misfits does not count.
 * 3) There should be some sort of interaction between the two characters. Having two stories each where the male and female are the hero of their own tale does not count.

Anime and Manga

 * Happens quite often in Studio Ghibli productions:
 * Kiki and Tombo from Kiki's Delivery Service.
 * Sheeta and Pazu from Laputa: Castle in the Sky.
 * Howl and Sophie from Howl's Moving Castle (anime), also occuring in the novel of the same name.
 * Arrietty and Sho in The Borrower Arrietty.
 * Umi and Shun in From Up on Poppy Hill.
 * Mary and Peter in Mary and the Witch's Flower. Considering that the production studio Studio Ponoc descended from Ghibli, there's no surprises here.

Film

 * Buttercup and Westley in The Princess Bride (film)

Literature

 * Sophie and Howl from Howl's Moving Castle (novel)
 * The unnamed boy and Arrietty in The Borrowers
 * Morrigan and her best friend Hawthorne in the Nevermoor series.