From Yuha scanlations:

A lone tengu witnesses how a student is getting mugged by a delinquent, but instead of helping, he asks the delinquent to teach him how to be like him. Sunao has always been criticized for being too kind for a tengu, so he decided to search for a human delinquent who could teach him about the ways of evil. Touya tries to refuse at first, but after seeing how naive Sunao is, he can't bring himself to ignore him.

Color 4-koma.

Pixiv Comic