Cactus Tears's manga / #teacher x student(17)

A new teacher has arrived at a school full of delinquents. He's meek and cute as rumors appear, but seems like his personality is a bit different.

Chiaki avoids his math teacher, Chiba, since he does not want to be tutored. One day he forgot his phone so goes back to school and sees his math teacher having sex with the PE teacher. Chiaki took a photo and decided to blackmail said teacher but to no avail.