Yuuto Amakawa, who suffers from severe allergies to felines, spends his mornings tending to his runny nose thanks to his friend Rinko's cat. However, on his sixteenth birthday, things go haywire as not only Rinko's cat but also his hormones trigger his allergic reaction. In an unexpected turn of events, a voluptuous sword-wielding cat spirit named Himari appears before him, vowing to protect Yuuto, who has become the target of vengeful spirits. With impending danger looming over him, it's apparent that Yuuto's allergies are the least of his concerns, and he will need Himari's assistance if he hopes to celebrate his seventeenth birthday.
