Omamori Himari.

The slapstick romantic comedy centers around an ordinary 16-year-old high school boy named Yūto Amakawa who is protected by a spirit—specifically, a beautiful, sword-wielding cat girl spirit named Himari. Yūto is descended from a family that has subjugated demons since time immemorial. The charm that once protected him is now impotent, but fortunately, at that same moment, Himari appears before him as his new guardian.