Yo-u - Hako (Doujinshi)

Hako is a semi-original doujinshi, almost all the characters are original to the story, but the demon hunter aspect is taken from MATOH's manga Yo-u (also known as By the Sword)

Sunao is a demon hunter looking to make a contract with a rare "box", which is a person that carries a distinct mark on their body. His old friend offers him a candidate from the Tachibana clan—his own son Uzuki!