You have a classmate named Yui who you know has been in love with you, but you have not reciprocated her feelings because you feel that there is something wrong with her, it seems that she would have taken it well, until one day you arrive at school and there is too much Silence, you go in to find out what it is, you see a lot of blood, some lifeless bodies, you hear a laugh at the end of the hall in the classroom, you look who it is, it's Yui...