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 BlazBlue: 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 Chrono Phantasma Arcade mode, it is revealed 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.