From Bliss:

Motoki was originally an ordinary guy with an ordinary life. Soon, however, Motoki starts noticing that things are changing in himself and his surroundings. His bad eyesight is cured, and suddenly he becomes prettier. As if in response to this mysterious change, two strange men appear in class, Shidou and Kubota. His classmates tell him that they have always been there, but he has no recollection of them. Then he finds out that both of them are after his life, and planning on "devouring his heart."