Any where the the leads are childhood friends. The male lead loves her, but must deal with the fact that another guy is in the picture. She only see him as a childhood friend and that brings him agony. Eventually the female lead realizes her love for him and they get together.

Preferably the male lead doesn't have another love interested besides the female lead, but the female lead does.

There's one called "that man later on", but uh well the female lead love the male lead, but fall in love with another man, leading to heartbreak on the male lead

in the end, the male lead also does not love her anymore and have harem with many woman

- i think there's this manga where the female lead lose her memory and go with another boy, in the end she regained her memory and married with the male lead(the art and story are kinda crap to be honest to the point i forget the title and it was teen love manga).

-Skip beat also a good manga where the female mc got betrayed by her handsome childhood friend, in the end she somehow have relation ship with another handshome guy and her childhood friend was jealous as fuu and decided to steal her away(no the manga still ongoing and the female lead did not end with that bastard guy who dump her)

skip to the point there's one manga that fit it perfectly..............

called break blade

but the male lead and female lead are not childhood friend, there are classmates in academy. The male lead have inferior complex, in the world people can use a stone for daily uses like you need to control the stone to active lamp,driving car(it use stone to control the car), and other daily tools. Our mc was a special case where he can't use the stone power where normal people could. So our mc can't even do shit and feel the female lead will be happy by marrying his best friend.

the male lead reject the female lead confession, female lead married with the male lead best friend, and he was a king, so the female lead become a queen.

the male lead who was in far remote area got called back when his best friend(the king) called him back and asked him to pilot a mecha where only him can use it(it did not powered by stone and no one can control it, it suggested only powerless people like MC can control it).

MC meet with the queen, some drama and in the end the queen say she loves him and mc decided to accept it. The king actually jealous but know that the queen did not love him(it implied they did not shared same bed room and never have sex in the first place so the queen is still virgin). And the king decided to give up his love to the queen and let MC with him. The queen married the king to make the MC jealous , and told the king , she married him so she can get funds for her experiment, the queen was a scientiest anyway and the king agrees that their marriage is just for show only.

Manga still ongoing anyway and the authour kinda have slow update on it because he have some problem in his lifes(i think he was sick or such, CMIIW).

Skip Beat for what its worth.

________________
Hobbies include impersonating fictional characters and sucking on ketchup packets.