The greatest and most awful evil in the schoolboy code in a classic school story. An informant has sinned against the Nakama and will forever receive a Mark of Shame. This can be handled in various ways. Sometimes the Aesop of the story is that there are times to inform as when the other student is cheating or "doing something harmful to himself". In the Crime and Punishment genre, this is the most important part of Honor Among Thieves.
Hello, Unknown Troper. You'll need to get known to lend a hand here.