I would recommend Omamori Himari.
Here's the description from Wikipedia (no spoilers)-
Seven years ago, Yuto Amakawa's parents died in a car accident, leaving him alone without a single relative. Ever since then, his childhood friend, Rinko Kuzaki, has woken him up, cooked for him, and generally takes 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).
From the day of his 16th birthday, his charm is said to not be able to protect him from evil spirits anymore, and Himari--a cat spirit samurai girl and demon huntress who, aside from wanting to copulate with him madly, swears to protect Yuto--was activated as his bodyguard, and appears in Yuto's life. There is only one small problem: Yuto has a severe allergic reaction to cats.
Genre-Action, Supernatural, Romantic comedy, Harem
Hope this helped
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