well if you want innocent, slow burn, sweet and emotional damage i recommend dont say you love me. personal favourite since i got attached also the mc realization and despair really hits.
https://www.mangago.zone/read-manga/king_s_maker_triple_crown/
Season 1 and 2 are masterpieces. Season 3 is trash, drop it at that point if you don’t feel like it.
Mature audience though.
Ooops, can't read, it doesn't start with them being kids
Hellu BL recommendation of seme and uke being childhood friends with story starting from them being kids ^^