Both are korean psychological thrillers about manipulation, power imbalance, obsession and obsessive love, unclear motivations and twisted characters that dont hesitate going to extremes. Both include taboo love triangles and age gaps and are pretty dark.
Dark, psychological thrillers, school setting, taboos, twists, manipulation, societal issues, unclear motives, violence... like misbehavior could have been a girl from nowhere episode in a different universe if youd flip the genders.
Both movies include a teacher-student relationship, infidelity and a main characters whose actions are understandable but frustrating... the vibes differ alot, however. Misbehaviour is a thriller and Yong Soon a slice of life drama.