Patient Childhood Love Interest

This is a character type that shows up frequently in Harem Anime and Visual Novels.

It is usually a girl, who grew up together with the main character, practically since infancy, and has been always in love with him, but instead of taking the initiative to become his girlfriend, she decided to take it slowly, developing a Like Brother and Sister relationship with him. In the most stereotypical examples, this trope is usually first demonstrated by a scene of her routinely visiting him in the morning, waking him up, walking to school with him, and giving him a lunch box full of delicious food that she prepared.

Basically, for the uninitiated observer, it would seem like they are already dating, and even those who know better, like their parents, or best friends, expect that they will eventually start dating and get married.

At this point, the Harem plot or Love Triangle starts, and in face of the new rivals she realizes that it's time to get serious. Hilarity Ensues, sometimes involving fights over her earlier "privileges" like feeding the protagonist, or as a trump card, bringing up some sort of Childhood Marriage Promise.

Often a Girl Next Door, even more literally than that trope describes, living close to the protagonist.

In terms of personality, she tends to be either a Yamato Nadeshiko in training, as evidenced by their cooking skills, serene patience, and the serving, yet guiding the boy at the same time, or the long friendship turns her into One of the Boys, a Tsundere who seems to be Vitriolic Best Buds with the boy.

If she is successful in breaking out of the Friend Zone, she becomes a Victorious Childhood Friend, if she fails, she becomes the Unlucky Childhood Friend.

In that thing we call Real Life, this sort of situation is very rare, mostly due to the Westermarck effect; people who have known each other since they were small children tend not to fall for one another because they literally have more of a sibling relationship. There are exceptions to this rule, but they're very rare (and, sadly, almost always one-sided). Typically, the earliest you can develop a proper "crush" on someone is your "pre-teen" years; works that posit an introduction of the couple prior to this can push the bounds of feasibility for many viewers.

Subtrope of Childhood Friends. See also Childhood Friend Romance for the more generic trope about people who knew each other since childhood falling in love.

Anime & Manga

 * Anaru from Ano Hana.
 * Manami from Asobi Ni Iku Yo.
 * Mayu from B Gata H Kei.
 * Misaki Etou from Dragon Crisis.
 * Kirie from Girls Bravo.
 * Infinite Stratos has, unusually for the Harem Genre, two Patient Childhood Love Interest characters. The protagonist even classifies them as " " and "Patient Childhood Love Interest #2", based on the time they met each other. The first is a Tsundere, the second a Yandere.
 * From Kimi Ni Todoke has a rare male version has Ryuu and his crush, Chizuru, she also is one as well, to his older brother.
 * Mimi from Lovely Complex intentionally assumes this personality when around Ootani.
 * Klan Klein to Michael from Macross Frontier.
 * Haruko from Maken Ki.
 * Asuka is this in one of Shinji's dream sequences in the last episode of Neon Genesis Evangelion.
 * Omamori Himari starts with Rinko in the role, but it turns out Yuuto had an Arranged Marriage and Childhood Marriage Promise with Kuesu before his memories were sealed and lets not forget Himari herself.
 * Subverted with Iroha from Oniichan no Koto Nanka Zenzen Suki Ja Nai N Dakara Ne, for she is VERY Clingy.
 * Manami from Ore Imo.
 * Sohara in Sora no Otoshimono.
 * Isana from Yumekui Merry
 * Rihoko from Amagami
 * Shirayuki from Hidan no Aria
 * Fujioka and Kana have been friends for awhile and he has a longstanding crush on her. She's so Oblivious to Love though that one starts to wonder if he should just give up. Given how popular he is with the ladies though, he'll probably catch his break once she hits puberty.
 * Ringo from Air Gear, where the protagonist Ikki actually lived for years in the same household with her and her sisters (the eldest of which, Rika, was promoted to parent), so they were almost literally Like Brother and Sister.
 * Takashi in Highschool of the Dead, a male example
 * Emily from Gundam AGE.

Fan Works

 * Miho Fukunaga of Milky Planet Pretty Cure is this to her closest friend, Toshi. His mother died when they were both young, so she acted as emotional support for him while slowly developing more romantic feelings towards him. Unfortunately, he remains oblivious to her intentions, and things only get worse when he falls for one of the exotic new transfer students...

Live Action TV

 * A non-Japanese example; Willow is this to Xander in the first seasons of Buffy the Vampire Slayer.

Video Games

 * This is pretty much Shana's attitude towards her love for Dart in Legend of Dragoon. It takes the rest of the party talking some sense into Dart before he finally reciprocates.
 * In Ar Tonelico, Shurelia's cosmosphere has Aurica as this. At one point, she confesses her love to Lyner. He has to reject her in order to advance the plot of the cosmosphere. If he accepts, Shurelia will complain and force him to redo the level.
 * To an extent, at least to the shippers, The Legend of Zelda series has Saria and Ilia.
 * The actual game has Ruto, who still considers herself your fiancee after the seven-year Time Skip.
 * Elements of this are played with both Cloud and Tifa from Final Fantasy VII. While the former's interest in Tifa isn't revealed until later into the game, the latter is the more obvious one being Cloud's staple childhood friend who has feelings for him, but it's subverted in that Tifa never really noticed him until after he left to join SOLDIER.

Visual Novels

 * Akari from To Heart, who contributed to the popularization of this archetype, especially the waking him up in the morning part.
 * In Cross Channel, the Genre Savvy Taichi comments that Nanaka's personality fits the Patient Childhood Love Interest trope, so it must be a flaw in the plot that she isn't really his childhood friend.
 * On the other hand, Youko is this trope deconstructed, and Taichi sees her as more of a Yandere Stalker With a Crush than anything.
 * Kei Shindou in Ef a Fairy Tale of The Two is a classic Tsundere variation.
 * Kaede from Shuffle. Sia and Nerine are childhood friends too, but Kaede's the one who fits the definition to a T.
 * Brass Restoration has a rare twist on this where the childhood friend, Minori, is a Cloudcuckoolander. Much humor is milked from the way she seems to follow many of the traits in the trope description, in the worst ways possible, such as making lunch for Ryo...except it's all rice.
 * Mizuka Nagamori from ONE ~To the Radiant Season~ is probably as straight as an example as it gets, possibly even exaggerated, considering the extent to which she takes care of protagonist Kouhei Orihara, who is a troublesome combination of a Jerkass and Cloudcuckoolander.
 * Da Capo has Sakura Yoshino, who's actually the protagonist's cousin but often called such by him. His adopted sister Nemu has more of the stereotypical characteristics of this trope, though - waking him up in the morning, going to school, long standing love, etc.
 * Subverted with Otome Katou from School Days, who triples as none other than Alpha Bitch and Jerkass.
 * Sumika from Muv-Luv to Takeru. She's content with their masochism tango until the very aggressive Meiya came into the picture. Meiya herself may also count even though she wasn't with him for most of her life.

Western Animation

 * In Danny Phantom Sam had been Danny's friend since they were little kids, and despite her obvious attraction to him she Can't Spit It Out until The Final.