The Protection Sword is an specially-forged, ages-old sword with writing inscribed on the blade. It is a tool of the Tsuchimikado Family.
By absorbing the aura within the user's body, it becomes capable of withstanding and repelling even an Tsuchigumo with a single swing in its initial state.
In the anime, by invoking the blade with an incantation and blood, the blade becomes imbued with the power of Indra and capable of using blue flames.
Incantation: "Praise be the Buddhas, far and wide! Praise be Indra, I call upon thee!"