Sealed Armament: Izayoi

The Sealed Weapon Izayoi is the weapon of choice for Tsubaki Yayoi. The Izayoi is kept under a special lock that can only be opened from the blood of a person from the Yayoi Family. Tsubaki needed the Izayoi to combat both Jin Kisaragi and Noel Vermillion, since they both possess Nox Nyctores class weapons. The Izayoi takes the shape of a short sword resembling a quill tip and a book-like shield. However, it can change its shape for some of Tsubaki's attacks.

The Izayoi has a negative side-effect: as it allows its owner to control light, it steals the light from the user's eyes. Due to this, using the weapon for an extended period of time will cause the user to go blind. The fact that it causes people to go blind during the course of Continuum Shift is told in both Story and Arcade Mode. As a matter of fact, Tsubaki is told numerous times to get rid of it. It is also revealed in Tager's Help Me, Professor Kokonoe! that along with its wielder's light, it draws in all waves within the electromagnetic spectrum, including the radio waves received by Tager's radio, allowing the weapon to interfere with radio signals.

It is revealed that Hazama's primary purpose in manipulating Tsubaki to fight her comrades was to gather its power until it overwhelmed her, bringing it under his control, and then creating a space through it that neither Takamagahara nor the Amaterasu Unit were able to observe.

In Phase Shift 4, it was revealed that the Izayoi was wielded by Ayame Yayoi, Tsubaki's ancestor during the Dark War.

In a recent Famitsu scan, it is revealed that Izayoi is sentient, and is set to be made into a playable character as the true form of Tsubaki Yayoi.

In Iron Tager's Continuum Shift story mode and Ragna's Chronophantasma Arcade mode, it is explained that the Sealed Weapon Izayoi is actually a prototype to the Lux Sanctus: Murakumo, explaining that the latter's experience with the Murakumo Units was why Tsubaki stood no chance against him.

Trivia

 * In Tsubaki's bad ending, she dies due to the overuse of the Izayoi, as she mentioned that she already knew that it will take her life. However, this is not canon. In Noel's arcade mode, when she faces Hazama, he comments on how Tsubaki's strength is "fading", implying that eventually the Izayoi may kill her.
 * The name Izayoi means "sixteen-day-old moon" in Japanese. A sixteen-day-old moon has just passed its fullest phase, so it is at this point that its brightness begins to decline. This is another clear reference to Izayoi's blindness-inducing nature.