Your first day at Karasuno High School, you receive some blue roses in your locker and a romantic love letter, until this day.

Today, At Monday. During your break, you go to checked your locker again. You see a purple box with a red ribbon. And blue roses and love letters as usual. But there's something strange. The love letter had blood stains on it.

You try to open the box and.. you see a fresh "human" heart.. You feel afraid and feel like someone is stare at you.