Damian and Jassie in Lavender Tea They were lost in the forest and had to stick together. When Jassie got hurt, the other boy nursed his injury and they became best friends. Damian started to develop a feeling he couldn't figure out, later realized it was love.
Rita and Tim in Gifts of Wandering Ice. Tim was assigned as a nurse to Rita after her surgery. They became best friends soon. Years later their friendship turned into love.
Played straight in Divine Bells with No-Woo's childhood crush on Mu-Hyang.
Played with in Kevin & Kell: Rudy and Fiona knew each other when they went to the same day care, but actually hated each other during their time together until Fiona moved away. Years later, when Fiona moved back, they ended up dating. Victorious Childhood Enemy, maybe?
They did not remember any of this until their former teacher told them about it.
Played straight with Bruno and Corrie, who first got to know each other when Bruno, on his first hunt, made the "mistake" of talking to his prey.
Alan and Beatrice from The Dreamer. Alan and Beatrice have known each other since Beatrice was in her early teens.
Then, once Justin finds out how the problem started and finally forgives her...she's gotten over him.
Another interesting case is Sarah and Elliot. Their parents are friends and they had play-dates before they were old enough for school. They've been close all their life, and when they're juniors in high school, Sarah confesses her love for Elliot and they start dating shortly after. Nearly a year later, Elliot realizes he loves Sarah "like a sister" and decides he wants to be "just friends". Sarah was actually planning to "just friends" him at the same time, but for different reasons, like frustration over the lack of romance and physical intimacy. After some awkwardness, the breakup ends up being almost unbelievably amicable.
When Axe Cop was still in fighting school, he had a secret crush on the then-Water Princess. It was so secret, he didn't even realize it until he was grown up. And since he was 100% compatible with every woman in the universe, of course the feeling was mutual.
Axe Cop: Oh yeah... I'm in love with the Water Queen. I better ask her on a date.
In this very emotional slideshow of comic panels, Life Isn't Perfect, the boy stands up to a girl who is getting bullied. After being bullied also, the girl returns the kindness to him and they become best friends. They stick together, fall in love, and get married, then emotional events roll in...
Looking for Group: As a young boy, Cale rescues a girl named Shora from an attack which destroyed her village (or rather, Cale nearly got himself killed trying, only for someone else (heavily implied to be Richard) to save them both). The pair subsequently grew up together at the monastery where Cale was trained, fell in love, and married. Unfortunately, this worked against the plans of the Archmage, and Cale's master was ordered to end their relationship. Shora was forced to cheat on Cale with another student at the monastery, and a heart-broken Cale left her. Unknown to Cale, to ensure he had no further reason to return the Archmage then forced Cale's master to murder Shora and clean up the loose end.
Dominic and Sarah from Unreality initially met when they were respectively 10 and 13, and within a couple years they became a full-on Romantic Couple!
Ebony Larsson and Siobhan Pattinson from the Maddie and Outsiders series of comics. The pair started as friends when Siobhan moved to the Isle of Hue when she was seven; where Ebony was already living. The pair got to know each other, with Siobhan teaching Ebony how to speak and read English while Ebony taught Siobhan how to have fun and be mischievous. Things became complicated when the pair discovered they were attracted to each other, Ebony accepting her sexuality while Siobhan refused to accept it. After having a fight, the pair did make up, but decided to keep Siobhan's bisexuality a secret by pretending to hate each other for two years. After the intervention of their new friend Maddie, the pair reconciled and confessed their love for one another, and are now absolutely devoted.
Aisopos: Bri and Aesop, who knew each other ever since they were 10 years old.