Kawaikunai Aniki wo Aegasu Houhou

Overview

A playboy college student who doesn't run out of lovers, Jin's stress relief is kissing his foster brother! An ordinary big brother who's adopted, Souji, who plays the good kid and doesn't get angry no matter what is done to him. The only thing that upsets this big brother is the unexpected kiss. The mask of the older brother who never shows his true self was finally peeled off... Or so he thought but... A sadistic type yandere (sweet and gentle yet brutal) younger brother x kojirase (someone who's not confident about their self) type ill-fated older brother, and their forbidden-obsessive love!!

Source: AniList