The demon blade, Masamune, is an extremely dangerous weapon and Tsubaki's older brother. He wanders around, possessing others to use him as their weapon to collect any soul he wants. He speaks using ancient words and likes to write haiku. He plays on the fears of others to possess and use them until he takes over their soul. He believes only the strong survive and the weak live only to serve the strong. He developed this way of thinking when Tsubaki inherited the family's multiple weapon forms. He considers himself more worthy than her and believed that he should have gotten the multiple weapon forms. He later lets Tsubaki defeat and absorb him after he sees that she really does care about him. Which gives her his katana form and all of his abilities, simultaneously being the first soul that Tsubaki successfully absorbs. He now resides deep within Tsubaki in the form of a large deer.

Attacks: He cannot use any attacks until he has possessed someone to wield him.
- Soul Possession: Used by demon blades to overpower and control the soul of its user.
- Shadow Puppet: Used by Demon Blade Masamune to control the shadow of the person he possessed for pincer attacks (the puppet can only say shadow).
- Puppet Strike: By folding the Shadow Puppet onto the blade, Masamune can create a far reaching lunge thrust.
- Split Branches: After the Puppet Strike, large spikes come out from the shadows body to skewer the enemy at close range.
- Puppet's Rain: By using multiple Shadow Puppets to restrain his enemy, Masamune stabs his enemy.