Chain

A mysterious person who appears out of nowhere after each murder occurs. Apparently he is in the same school as the heroine, but in a special class. Everyone in that class barely appears at school so she has never seen him before. Later it is discovered that he lives one street further away from the heroine. He does not speak much but when he does, it is only for important matters or blunt comments. His appearance and glance give a cold vibrance that makes an average person tremble. Since he is a mysterious person, it makes the heroine wonder if he has something to do with the murders. [From official site]