Mai Kawasumi, amongst the graduating students of Yuuichi's new high school, is a mysterious girl. Due to her disregard for what's considered "normal behavior," she's viewed as a delinquent by her peers. She holds a very close relationship with her fellow senior, Kurata Sayuri, and can usually be seen with her most of the time.
When Mai was still a young girl, her mother fell ill. During this time of despair, Mai discovered a great inherent power; the ability to heal living creatures at will. This power rose her to child fame; however, the townspeople grew to fear her power as it was unusual. As a result, Mai was ostracized by everyone except her mother, and soon they were forced to move to another town. Mai was told that one day she would meet someone who would be able to put aside her powers and become a great friend, and that friend was Yuuichi.
However it wasn't long before Yuuichi had to leave the town and return home. This caused Mai grief, and in her desperation she began to fabricate a story about monsters invading their favorite place to play together: a field of wheat. Later, the school was built on that field, and Mai continued to walk those grounds late at night, sword at the ready, fighting off the demons which manifested from her very own powers.
In the present day story, Yuuichi first meets Mai in a school corridor at night. It's after then that Yuuichi begins eating lunch with Sayuri and Mai on a regular basis. With Yuuichi and Sayuri's support Mai avoids expulsion from school, between broken windows from her nightly demon hunting and a battle that completely demolishes the school dance.
Eventually, Yuuichi would be at Mai's side in her final stand as she raged against the demons for hurting Sayuri, and defeat the malevolence generated by her past. She attempts to take her own life afterward, but fails and ends up recuperating in a hospital with Sayuri.
