Dong Eun’s visit made the teacher enraged and make a fuzz and neighbors might have heard her mention he ruined her life. The son was worried what his dad did in the past would be spread out and ruin his and his son’s reputation and teacher exam result. The teacher’s death would probably stop people from spreading about and investigating the teacher’s dark past. His son wanted his sacrifice to save his image till the end of his life. I think the teacher deserves it! I was shocked at him more than the bullies for being a bully teacher!