Its school life, it's boy A, boy B and girl, inshort love triangle. the A and girl are childhood friends, boy A and b and girl are friends too, since boy A has some illness (is it asthma??) girl is always there. the boy A likes the boy B, and the girl also like the boy B, then the childhood friends announced each other as rivals, but then the girl realized the one he truly likes is the boy A, at the end the girl confessed to his childhood friend but got rejected then the boy A also confessed to the b but got rejected too.

I think I've heard of this similar premise somewhere... is it 10th?
https://www.mangaupdates.com/series.html?id=153362