[Mitsuya] Ane Kyōshi | Sister Teacher (Neechan to XXX Shitai no) {bfrost}

Dumped yet again, hapless student Ryo drags himself home to the one woman who's always watched over him — his voluptuous older sister, a bespectacled office lady whose business suit barely restrains her huge breasts. Her consolation turns ravenous fast: she kisses him breathless, takes his virginity, and swears no other girl will ever have him now that she's claimed his first time. Even their secret trysts at his school continue afterward, sealed with her smug confession that she doesn't care about the rules — after all, she's his sister.