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Anything by Amamiya
Can't remember if either is particularly possessive, but they are childhood friends and it's one of my favourites. Cute and fluffy yaoi:
https://www.mangago.me/read-manga/tomodachi_ijou_no_koto_shitai/
One shot about two childhood friends who gets into the nasty bc of some sex toys. Seme has a bit of a possessive vibe:
https://www.mangago.me/read-manga/nigenaide_rinjin_kun/
I just started reading it! Thak you this is exaclty what I was looking for !
A bl that is shortish and has a possesive lover that are childhood frineds ?