Himitsu Kichi ni Aijin

Synopsis

An invitation to a secret base is sent to Tetsuji, whose students call him "Mambo-sensei" behind his back for his listless demeanor. While suspicious, he arrives to find a young man he doesn't recognize. "I'll answer a question every time you do have sex with me." What is the motive of the man's audacious invitation...?! (Source: Gentosha Comics, translated)