The Legend of Onikirimaru(2013)

Onikirimaruden

A demon boy who lacks horns on his head wields the cursed blade "Onikirimaru," the one weapon that can slay a demon, in a never-ending battle with the demons that haunt Japan during the age of the samurai. Behind the stories of Oda Nobunaga, Toyotomi Hidetsugu, Ishida Mitsunari and the other famous generals of the Japanese civil wars lurk secrets and demons... An astonishingly deep story about these demons and the sword Onikirimaru! And this also includes the secrets of Onikirimaru's birth, which readers have always wanted to know. The legend of Onikirimaru explains clearly how Onikiri was born, and the hidden secrets of his past. Behold the battle between the darkness of the age of the samurai and Onikirimaru!

(Source: Crunchyroll)