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 box bento that she made just for him.
To the uninitiated observer, it'll seem like they're already dating, and even those who know better, like their parents, or best friends, expect that they eventually will.
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 the 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.
Truth in Television, but only to an extent. There's a theory known as the "Westermarck effect" that claims that people who grew up together before the age of 6 are likely to become hardwired to think about each other Like Brother and Sister. So, the characters wouldn't be able to fall in love if they'd really known each other since infancy.
- Ringo Noyamane 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. She seems to have the upper hand now though, as Ikki's Link Tuner.
- Anaru and Tsuruko from Ano Hana The Flower We Saw That Day. They may have chances to get together with the guys they like, Jintan and Yukiatsu, by the end of the series. But only after an emotionally-exhausting journey for EVERYONE in their group.
- Both Yayoi Aoba and Sanae Nakazawa are this to Tsubasa in Captain Tsubasa. Yayoi moves on and stays Just Friends with him and might end up with his friend Misugi instead, while Sanae eventually switches to Victorious Childhood Friend when she and Tsubasa are teenagers and they end up married.
- Ami Kurimoto is this to Junta Momonari in DNA², and it's actually a huge plot point: as his childhood friend, Ami has come to know Junta so well... that she is completely immune to his Mega Playboy side and, even more, is disgusted by him. This means she loves the real Junta, awkward and childish and all, rather than him as the super suave and seductive Mega Playboy.
- Almost all of the main love interests in Detective Conan, especially Shinichi and Ran, Kaito and Aoko and Heiji and Kazuha. Shinichi and Ran are already a couple now (sort of), but the other two are just too stubborn to admit they're in love. Though it looks like Kazuha and Heiji are surely going that way.
- Girls Bravo: Subverted in Kirie's case. Her first and only real attempt to get closer to Yukinari is in episode 4, where she fixes him a box bento in hopes of going on a lunch date with him. Which fails due to a series of unforeseen events and, with Lisa now entering the picture, along with Miharu, Kirie knew she didn't have a chance. So she calls it quits and settles for just being friends with him.
- Sohara in Heaven's Lost Property. She's Tomoki's childhood friend, lives next door from him, often goes to his house in the morning to wake him up and despite usually beating him up with karate chops, she very obviously loves him and is always looking after him.
- Highschool of the Dead zigzags the trope with Takashi and Rei, who both fill the role at different points in the series:
- They used to date back in middle-school, but broke up after Rei was forced to repeat her junior year. During that time, Takashi began to ignore her since she wouldn't talk to him about it, causing her to think he had abandoned her. So she began dating Takashi's best friend, Hiashi, because he provided her with the emotional support she needed.
- Despite the above, Rei still harbored feelings for Takashi, while Takashi tried to hide his resentment over Hisashi's relationship with her. But Hisashi was bitten during the outbreak and briefly became one of "them", which forced Takashi to kill him. Rei was left conflicted by her resentment towards Takashi over Hisashi's death and her lingering feelings for him. She soon decided on the latter and now hopes to rekindle what they once had.
- However, the anime version complicates the issue with additional amounts of Ship Tease between Takashi and Saeko, which wasn't seen in the manga. Leaving Rei in the unenviable position of having to compete with Saeko for Takashi's affections. Though in episode 11, she and Takshi hook up again.
- Infinite Stratos has, unusually for the Harem Genre, two Patient Childhood Love Interest characters. The protagonist even classifies them as "First Childhood Friend:"note " and "Second Childhood Friend", based on the time they met with him. The first is a Tsundere, the second a Yandere.
- Kimi ni Todoke has a rare male version; Ryuu is this to Chizuru. Strangely enough, she is also an example of the trope herself...but towards Ryu's older brother.
- Mimi from Lovely Complex intentionally assumes this personality when around Ootani.
- A possible interpretation of Koyuki's feelings for Ginta in MÄR. This attitude is carried over into Snow as well, even though she didn't grow up with Ginta. The anime ends with Koyuki and Snow merging into one person to be with Ginta followed by a rather touching moment as they walk home together, their arms locked.
- Fujioka and Kana from Minami-ke 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.
- Frau Bow from Mobile Suit Gundam, whose name actually translates to "wife". There's a lot of focus on how much she cares for and supports the protagonist, her best friend Amuro. He seems like an Ungrateful Bastard a lot of the time, but he does finally call her "boku no suki na Frau" = "my sweet Frau" at the end. No, their relationship isn't any less complicated in the sequel.
- Hinata with Naruto is a bit complicated. She has always admired him since the day they met, and she was the very first person to acknowledge him for the way he is and care for him for he was. However, her feelings of admiration did not become romantic until she was older. While Naruto was among the first people to acknowledge Hinata in the Chunin Exams arc, his cruddy upbringing meant he wasn't able to grasp Hinata loving him romantically. Hinata later confessed her love to him in the Invasion of Pain arc, and although Naruto never directly mentioned her Love Confession, they started to have more significant Ship Tease afterwards, beginning in the Fourth Shinobi World War Arc. She did not stop loving him, even if it took a long while for Naruto grasp the feelings. In the canon movie The Last: Naruto the Movie, Hinata's patience was finally rewarded—Naruto realizes that he's in love with her and he reciprocates her feelings. The movie also Implies that Naruto had been in love with Hinata for quite some time but was unable to recognize nor understand his own feelings due to his severe self-esteem issues. At the end of the movie and in the epilogue, Naruto and Hinata are married with two children.
- Jiraiya with Tsunade. He loved her since childhood but never took the initiative. This one is even more tragic, because it's Implied that she did grow to love him but was too afraid to get close to anyone because her loved ones, particularly her boyfriend Dan and younger brother Nawaki, had died. Jiraiya himself dies as well.
- Asuka is this in one of Shinji's dream sequences in the last episode of Neon Genesis Evangelion and the "Angelic Days" manga.
- 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 Onii-chan no Koto Nanka Zenzen Suki Janain Dakara ne!!, for she is VERY Clingy.
- Serena in the Pokémon anime. It took her a while to even bring up the first time they met (which Ash had forgotten), and is often patient and helpful towards her love interest, all while blushing and waiting for him to acknowledge her. Unfortunately for her, her love interest is Ash, one of the most famous characters to ever be oblivious to love. Though at least she gets the chance to give him what looks suspiciously like a kiss.
- In Puella Magi Madoka Magica, Sayaka quietly stood by Kyousuke side through his Career-Ending Injury-induced depression, but he proved remarkably Oblivious to Love. Eventually, Sayaka makes a contract to become a Magical Girl in exchange for Kyousuke getting healed. However, Mami specifically asks if this is really a Selfless Wish, or if Sayaka just wants to feel like Kyousuke "owes" her now. Eventually, Kyousuke hooks up with Hitomi, who unlike Sayaka, actually confessed her feelings. This, paired with Sayaka's huge and complex issues, goes very badly.
- RahXephon has Haruka Shitow... or at least had, until she and Ayato were separated when Tokyo Jupier was formed. When they met again, Ayato stayed young and Haruka had grown up, plus he lost his memories of her for very complicated reasons.
- So, I Can't Play H!: Mina has nursed an unrequited crush on her neighbor, Ryosuke, since they were kids. But she's so shy, that she was unable to work up the courage to tell him until they were in middle school. In episode 11, he explains that he doesn't reciprocate specifically because she's his friend. Were it not for that, he would've said "yes" and even married her.
- Philuffy in Undefeated Bahamut Chronicle is this to Lux. When they were children, she supported him when his family was thrown out of the palace and hsi mother died. In the present, she's the least aggressive out of all the girls - for example, when Lux has to go on a date with her and two other girls in the same day, her date consists of letting Lux sleep and recover from the day's work.
- Hak from Yona of the Dawn resolved from very early on to stay on the sidelines to allow Yona to pursue Su-won. It...didn't work out well. After which he does actually attempt to pursue her in earnest for a while, but soon decides to give up when she asks him to stop "joking" with her. It takes about a hundred chapters, but she does eventually come to develop and realize she has feelings for him.
- Tsubaki from Your Lie in April has liked Kousei since childhood, but their relationship has always been sibling-like. She's fine with it until Kousei begins to become closer to Kaori.
- Isana from Yumekui Merry. Clearly has very strong feelings for Yumeji, and apparently has had them for some time.
- Deconstructed in the Homestuck fic I Will Not Let This Consume Me. Eridan is too afraid of rejection to confess his feelings. He ends up resenting his friendship with Feferi and pushing her away.
Eridan: I can't tell her, okay? I don't want to mess things up. What if I weird her out and she doesn't want me around anymore? What would I do then, Kar? No. I just need to think about it...clear my mind...think of the best way to approach this. Wait for the right moment.Karkat: What moment exactly? The one when she'll randomly reveal to you that she's been longing to touch you indiscreetly all along? Or the one when she'll finally notice you and fall for the red solicitations you're not even making because you're too scared? Answer me that. Because I can't even tell if you believe the rubbish that comes out of your mouth anymore.Eridan: What the fuck, Kar? I don't need this kind of bullshit from you.Karkat: Okay, sorry. But if you're waiting for me to tell you what you want to hear, you're talking to the wrong troll. Listen, dude, I get that it's pretty fucked up and complicated. But what's your plan? Wait your own feelings out? Wait for things to magically solve themselves?
- Chiyo of Despair's Last Resort fell in love with a boy from her childhood and decided to wait until they were older to confess. She never gets the chance. He dies of a terminal illness before she can.
- In The Miracle of Morgan's Creek, Norval and Trudy are childhood friends and at one point Norval confesses that he was always in love with her but couldn't spit it out all this time.
- In Preacher's Kid, Wynton has been patiently waiting on Angie for years, but she sees him as nothing more than a friend, and her father refused to grant permission to date her because she's too busy with the Lord's work.
- A variation in ½ Prince. Since Zhou moved away 8 years before the events of the story he found Lan in an online game and became her husband there, at least until she looses interest and goes on to a new game. When he finds her again in both the real world and the new MMORPG she switches to she's developed to the point of no longer wanting to hide behind a man, and he has to adopt a more aggressive strategy to win her over. He can't, and ends up losing her to Gui.
- Eva Luna had strong feelings and slight whiffs of the trope for Huberto Naranjo, the local Street Urchin and Jerk with a Heart of Gold, ever since they met as kids no older than 10. As a pre-teen, she was this to a T towards him, and was frustrated because he told her "Youre Just a Kid" many times which was a Jerk Ass Facade since he always held a torch for Eva but didn't want to admit it. When they did get together, they only saw each other counted times yet she pantiently waited for him. Unusually for the trope, Eva is critisized for it by her Cool Big Sis Mimi, who also knows Huberto from childhood and loudly wonders "What Does She See in Him?". And in the end, they break up amiably and she gets together with Intrepid Reporter Rolf instead.
- In The Good Student Nic acts like this to Dizzy. After they are separated he works his butt off to get accepted into the prestigious academy she intends. The plot unfurls from there.
- Initially, Tommy Beresford to Tuppence Cowley, who remained somewhat oblivious and insisted that she and Tommy were just good mates until the Love Epiphany hit. For his part, Tommy treats Tuppence as a friend and does not make the full extent of his feelings known even to the reader until she is believed dead and he launches into a "The Reason You Suck" Speech on a lesser suitor who claims to mourn her deeply despite having known her for a matter of days.
- Starflight from Wings of Fire is this to Sunny. According to Glory, Starflight had been in love with Sunny since they were little. However, when he confesses, Sunny is unsure of how she feels. She ultimately decides that they're Like Brother and Sister, and that their relationship is too familial, since they were raised together from birth despite not being actual siblings. It's implied that Starflight is now in love with Fatespeaker, but it's unknown whether he moved on.
- Willow is this to Xander in the first seasons of Buffy the Vampire Slayer.
- In British sitcom The Inbetweeners, Simon is this to Carli.
- During the run of the 11th Doctor on Doctor Who we find out that Rory was essentially like this to Amy Pond. They spent their childhood as friends, and as soon as they were old enough Rory fell hard for her and never even showed interest in anyone else. It was Amy that always had doubts and occasional longings for others, until they were actually married.
- The Flash (2014): Barry Allen has been in love with his best friend Iris West practically all his life, before he even knew what love was. He waited years for her to notice his feelings, but after she got herself a steady boyfriend, decided that he couldn't keep lying to her and confessed. Unlike most examples, Barry did try to move on from Iris — but none of his attempts ever stuck. It takes a while, but he and Iris finally got together in Season 3.
- This is Shana's attitude towards her love for Dart in The Legend of Dragoon. It takes the rest of the party talking some sense into Dart before he finally reciprocates.
- In Ar tonelico: Melody of Elemia, 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: Ocarina of Time's Saria and The Legend of Zelda: Twilight Princess' Ilia.
- The actual game has Ruto, who still considers herself your fiancee after the seven-year Time Skip.
- The Legend of Zelda: Skyward Sword has Zelda herself, who, living on a tiny floating island, naturally has known Link all her life. The game starts with her sending a letter via her Loftwing to wake him up for his graduation ceremony.
- 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 he was right about to leave their village to join SOLDIER.
- Tana from Fire Emblem: The Sacred Stones is this to Ephraim. She can be one of his two brides, but her feelings can potentially be swayed towards Cormag as well.
- In Fire Emblem Awakening, Cynthia is hinted to be this to Inigo. Whether she gets him or not, it depends on the player's strategies.
- Tia from Lufia II: Rise of the Sinistrals shows that this does not work; Selan, Maxim's destined love interest, beats her into a confession. The man doesn't even notice her feeling for him.
- In the first entry of the SNK Dating Sims Days of Memories, Boku to Kanojo no Atsui Natsu Athena Asamiya is both this and the local Idol Singer. (Not in the others, however.)
- Yandere Simulator is set to feature one of these as Yandere-chan's first rival for Senpai's affections. For bonus points, her name is Osana Najimi.
- Akari from To Heart, who contributed to the popularization of this archetype, especially the waking him up in the morning part.
- In CROSSCHANNEL, the Genre Savvy Taichi comments that Nanaka's personality fits this trope, so it must be a flaw in the plot that she isn't really his childhood friend. She's actually his mother.
- 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 Cloudcuckoo Lander. 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 Jerk Ass and Cloudcuckoo Lander.
- 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.
- Mashiro and Yuuri in Root Double: Before Crime * After Days, towards Natsuhiko. A young Yuuri even told Natsuhiko she wanted to be his bride. However, the two girls are close enough Childhood Friends that they can have a friendly rivalry once they both realise they have a chance.
- Mashiro, while initially having a One of the Boys relationship with Natsuhiko, falls in love with him while watching over his delusional state after Yuuri's apparent death and even does his cooking. Yuuri sacrifices her ultimate freedom for Natsuhiko's and can only see him once a year while he is unconscious, preventing her from furthering her relationship with him.
- Subverted with Otome Katou from School Days, who triples as none other than Alpha Bitch and Jerk Ass.
- Muv-Luv: Sumika 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.
- Sayaka Maizono from Danganronpa seems to be headed to this direction, even when she and Naegi knew each other mostly in passing. Subverted in that Sayaka had decided to frame him for murder in the Hope's Peak murderous atmosphere... but then she was killed instead.
- Mikae Morikawa from True Love Junai Monogatari. Very cute, a tsundere, and the main guy's childhood friend. And she has never forgotten the Childhood Marriage Promise they made.
- Tokimeki Memorial 4 has Miyako Okura, the boy's best friend and Info Woman. She can be unlocked as a Love Interest, but...
- 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 finale.
- Young Justice introduced Barbara as Dick's friend in season one, with a hint that she has a thing for him. Nothing really comes of this in the show, but the post-Time Skip issues of the tie-in comic have her this way. Dick even likes her back, but he's also a massive horndog, and she says that she's willing to wait until he matures a little more. (The end implies they may be Friends with Benefits, though.)