Fūinsha

Fūinsha is a sword crafted by Tsuyoshi himself after many years of training in Fūinjutsu. As the name suggests, it is a katana with the ability to seal "anything and everything" within itself. Anything that touches the blade of the sword will be sealed. However, any other part of the sword won't affect the target. The sword was designed by choosing a special hilt and sheath that wouldn't be sealed by contact with the sword. They were also crafted by Tsuyoshi. The sealing is done instantly as soon as the target touches the blade, they deform and look like a liquid substance, which is sucked into the sword. The capacity of the sword is infinite as it can seal as much as the user likes. Fūinsha is a black sword with a black hilt, sheath and even a black blade. Tsuyoshi said that he crafted multiple duplicates of Fūinsha, but kept the first one for himself. The other swords are to be given to those who are worthy of having them in Tsuyoshi's eyes.