Kotetsu is a young villager from the Swordsmith Village. He's cheerful and bratty. He is 10 years old. Like all of the residents of the Swordsmith Village, they all wears Hyottoko Masks. His ancestors built the battle doll Yoriichi Type Zero. It's the only memento his family has left, since he's an orphan. He is under the care of the Swordsmith's specifically Kozo Kanamori and Hotaru Haganezuka. The doll is used for training Demon Slayers, but throughout the centuries, it has deteriorated.