YOUKOSO! BL KENKYUU CLUB E

Not being able to pay his living expense, Sato, a poor college student turned to Kaname and Hata's help. They offered him an easy job with extravagant pay. Satou jumped in without asking for more details... And of course, it is not ended up well since he actually has to become an experiment subject for secret yaoi research! From anal expansion, nipple play, to S&M experiment⁠—Sato is slowly drowning to the BL swamp without knowing what his best friends actually plan...

(Source: Manga.Club)