The Teen Exorcist, Vol. 1 (manga)

Purge evil spirits, protect the princess… It's all child's play for this teenage exorcist!! Like his grandfather before him, thirteen-year-old Masahiro serves the Japanese Imperial Court as an exorcist. His predecessor isn't just anyone, though—he's the living legend Abe no Seimei! Meanwhile, Masahiro's stuck being called "Seimei's grandson." But the teenage exorcist has no intention of spending his days in his gramps's shadow, and his chance to prove himself may come sooner than expected… When he notices an insidious presence targeting the princess, will he finally get his turn in the spotlight?!

Volume 1 of The Teen Exorcist manga series by Minna Lin.