I Said I Love you to Death, Didn't I?

A boy named Aoi Asumori, a high school student with a peculiar constitution that can see spirits is secretly in love with his classmate Ai ichinose, who is very popular because of her bright personality. However there is a large number of spirits lingering in the background... Why are they coming after her? As an inexplicable incident creeps in, Aoi decides to become a hero that can protect her...