Suzue Shizuka appears, on the surface, to be an ordinary high school girl. Beneath that surface, she is the descendant of a great water spirit, carrying enough magical power inside her that if she does not release it regularly — through fighting other spirits at the school — she develops a fever and loses control. Her school runs two sessions: human students during the day, and spirit students during the nightly "Witching Hour," when youkai who may be thousands of years old attend class alongside her.