Witchcraft Works Vol 1

Witchcraft Works by Ryu Mizunagi. A Fantasy manga rated Teen, published in English by Vertical.

Honoka Takamiya is an ordinary high schooler, until he discovers that Ayaka Kagari, the most beautiful girl at school, is actually a powerful witch sworn to protect him. Suddenly he's at the center of a war between witches, and he has no idea why.