The manga is about a guy who's in love with his best friend/childhood friend. I believe the setting is in their adult age. After a few chapters their relationship progress a little bit until he meets his ex boyfriend (from high school I think) who he had to break up with forcefully back in their high school days. They were madly in love with each other but when the boyfriend's parents found out about their relationship, they had separate. Then now, when they met, his ex boyfriend tries to ask him out and wants to be with him again. The best friend was very jealous because the main character was spending a lot of time with his ex boyfriend and then I remember in the end the best friend and main ended up together but ... ANYWAY I JUST CAN'T REMEMBER THE NAME. I even google searched love triangle between childhood friend and exboyfriend but unfortunately nothing 😢 I wanna read this manga again cause I'm obsessed with love triangles 🤣

It's probably not what you're seeking, but I'll post since the premise is similar (and because you're obsessed with love triangles!):

Higouhou Junai by Fuwa Shinri