Omamori Himari

Yūto Amakawa is a 15 year old boy living by himself, with help from his childhood friend Kuzaki Rinko. He has been living like that ever since he was seven years old, that was when his parents died.
On the day of his 16th birthday as an old charm he has is said to stop working, but instead a strange cat spirit girl walks into his life, she swears to protect him instead of the charm. There is only one problem, Yuuto is very allergic to cats.