Its a story about a teacher and a student where the student confessed to the teacher but things are put on hold until his graduation. I know that seems a bit vague but the most I can remember is that the student had a pretty lazy attitude and that at one point in the story, they introduced...
All I remember is that its a psychological manga about murder and the main character has a knife collection or something similar. Sorry if my description kind of vague because it's a manga that was in my bookmarks when kissmanga was shutdown.