Kirihoushi

Kirihoushi (切法師) is a manga series by Yuuki Nakashima. It was serialized in Weekly Shonen Jump.

Plot
Long ago, humans lived in the midst of demons and other Japanese folk creatures. Only powerful warriors called "Kirihoushi" were able to compete with these monsters. Rintarou is a young apprentice Kirihoushi who decided to take the plunge, the day a demon took the life of his parents.

Since then, he follows the teachings of his masters, which is not easy when you spend your time dreaming of adventures, magic swords or damsels in distress.