The hentai manga Kyoushi to Seito to. And no, it's not another one of those generic hentai manga, it has plot. It's actually the 3rd highest rated hentai manga on MAL and the highest rated on Baka Updates.
SIR.... PLEASE TRY...." HATSUKOI SHINJUU " the male student was about to commit suicide just when the cute teacher with the same intention saw the student and thats where their lovey dovey comedy drama story began... its just that they look cute together