Yuuto Amakawa is severely allergic to felines, so he spends his mornings nursing a runny nose caused by his friend Rinko's cat. But on his sixteenth birthday, it is not just Rinko's pet that is aggravating his allergies (not to mention his hormones)! Himari appears before him: a buxom, sword-wielding cat spirit in human form, who has sworn to protect Yuuto, who is now the target of vengeful spirits! It is clear that Yuuto's allergies are the least of his problems—he will need Himari's help if he wants to live to see his seventeenth birthday!