
The kid himself says he touched him. (He also immediately knew what the marks on the MCs wrists were and what the training was). The teacher says he touched him. They're just trying to claim he didn't sexually harass him, which we all know is utter bullshit since the teacher is an adult and the student a minor. It can be nothing else BUT sexual harassment/rape of a minor. A CHILD.
100% is a pedophile

Tengoku more than likely taught him about bondage and/or how to tie knots assuming the student had questions about that rather than them having some sort of explicit bondage play (like with aoki), this seems to be another purposeful misunderstanding for the sake of furthering Aoki's suspicions and for comedic effect. Obviously not the job of a counselor IRL to teach anything bondage-related to a student, but in this fictional world featuring softcore-japanese-hannibal-lecter he's more-so in line with a clinical bdsm-friendly sex educator (in the case of students) than a predator; The whole 'tengoku-touching-students' thing is just bait for aoki who is his real target/interest. The reality of the situation and the intentions and thought processes of the characters are hard to miss if you don't pay closer attention.
He touches high school kids. The nurse definitely sexually assaulted minors. This is all very ikk. I don't really get how this one is so highly rated.