Pls help

I've been looking for this manga for a few days and I feel like I'm going crazy
It's a BL manga where the mc denies really hard that he has any tipe of sexual desire cause his sister is really open about sex and he gets embarrassed cause even classmates know his sister (i think she was a porn actress or something), except for this blond guy that sits next to him. One day the sister puts a condom in his backpack and it falls when raking out some stuff so the blond guy gives it back to him. Then I don't remember why but blondie goes to mc house and the sister left an onahole there I think, other things happen that ai don't remember too well, just typing everything I do remember