Masked Reunion (2019)

Yosuke Shintani left his hometown right after his high school graduation. He wanted to leave behind memories of his older brother who died in an accident and a teacher who was bad to the students. Now, Yosuke is back in his hometown due to a personnel transfer at his work. He decides to attend a school reunion and meets three friends from his high school days. Yosuke and the three friends kidnap their ex-teacher who punished the students with physical force. They beat him up and leave him there. Yosuke and his three friends thought it was a joke, but the teacher is found dead the next day.