Yata no Kagami (八咫鏡 Yata no Kagami) is a mirror obtained by Ilyaelia Murometz during the Mt. Fuji Haunted Ground Treasure Quest. It is later given to Ikōsai Aisu in order to fight Kazuki. It is one of Three Regalia. If someone possesses the three of them, that person becomes Japan's King.
Out of the Three Regalia, Yata no Kagami represents the defense and protection of Japan's King. It is demonstrated in Volume 8 and Volume 9 when Aisu didn't take any damage from Kazuki's attacks. Despite being the Regalia with the absolute protection when it comes to attacks, it has a weakness that was exploited by Kazuki.
- Fuukyou Kaikon ― Mizukagami no Tate: One of the incantations of Yata no Kagami. It enlarges the mirror creating a mirror shield with the power to protect the user from any kind of attack that is reflected in the mirror. If the mirror is stained, the user loses the protection and the mirror cannot be used again until the stain is removed.
- Fuukyou Kaikon ― Youka Ippou: An incantation that fires a thick heat laser from Yata no Kagami.
- Fuukyou Kaikon ― Hika Issen: Yata no Kagami emits a pure white light resembling the sun that causes immense heat and light damage if caught in its radius.
- Fuukyou Kaikon ― Youka Issen: Another incantation of Yata no Kagami. The mirror releases a flash of light that can purify people and (possibly) Haunted Grounds.
- Fuukyou Kaikon ― Tsukuyomi no Kagami: An incantation that reflects the magic phenomena back at the enemy by first disassembling the attribute of the magic then reflecting the pure energy back at them.