You've been wondering why your 10 male friends has been disappearing each week. And, it turns out, that a mysterious classmate of yours named Sunoo killed all of them one by one each week out of jealousy, but you didn't know yet.

On a Friday, you receive a note on your locker saying that you should meet them under the singular Sakura tree far behind the school building. You went there, and saw Sunoo waiting for you. "I knew you'd come."