Kureha

Personality:
Unlike the disturbing rumors about him, he has a calm personality. He is honest and frank but the things he says or does might come off as slightly off. He seems to be attracted to the protagonist...

Rumor of Bloodthirsty Killer "Karakara-san":
They say after school, when you hear the sound of iron being dragged in the school building at dusk, don't turn around.
If you do, you will be asked a question.
If you can't answer it or give the wrong answer, you'll be killed.

Spoiler

His full name is Kureha Tendou.