Seven years ago, Amakawa Yuuto's parents died leaving him living alone without a single relative. Ever since then, his childhood friend, Kuzaki Rinko, has waken him up, cooked for him and generally taken care of him. The only thing he has from any relative is a mysterious charm, a red ball, given to him by his grandparents as a good luck charm (an omamori).

On the day of his 16th birthday, this charm mysteriously disappears, and into Yuuto's life walks Himari. A cat spirit-samurai girl and demon hunter who swears to protect Yuuto. There is only one small problem. Yuuto has a severe allergic reaction to cats! Hang on to your manga-reading chair as this slapstick love comedy with a bit of good ol' fashion demon hunting is about to begin!