Hagane Daido/Synopsis

History
In the past, Daido was a nameless but unmatched master swordsman. In the present day, Daido is incarnated by Kenjaku and participates in the Culling Game.

Culling Game Arc
On November 2nd, 2018, Daido roamed the abandoned city of Kagoshima in the Sakurajima Colony. He fruitlessly searched for a katana, eventually finding what appeared to be one stuffed in a box with toys. Excited, he pulls out the sword, only to discover that it is a DX Nichirin Sword, a toy. This disappoints him to tears.

On November 14, Daido and Rokujushi Miyo simultaneously interrupt the fight between Maki Zenin, Noritoshi Kamo and the cursed spirit that was Naoya Zenin. Upon seeing Maki's katana, Daido cries tears of joys and enthusiastically shouts "katana!!". Deciding to break the stalemate, Maki throws her blade to Daido. Upon catching the cursed tool, everyone nearby is overwhelmed by a fear-inducing sensation. They're not stricken by cursed energy, instead, they can feel Daido's sheer lethality with a blade.

Daido slashes the sword in Naoya's direction, who narrowly avoids the attack. Noticing that the sword is unmarked and has no guard, Daido realizes he is wielding a demonic sword and orders it to obey his commands. Maki tries to warn Daido about an incoming attack from Naoya but he easily avoids it. Daido asks Maki if they're facing some kind of evil spirit and she's confused about how he can fight Naoya without being able to see him. Daido states that he can see everything else around Naoya, which makes it the same as being able to see the cursed spirit. He then bisects Naoya with a single slash, surprising Maki. Daido asks why Maki didn't do that in the first place and she struggles to understand what she isn't seeing.

After Maki exits Miyo's Simple Domain, Naoya flies away to gain speed for another attack. As Miyo and Daido ready themselves for a fight, Noritoshi asks for their identities. They claim they're individuals who do as they want and their identities are of little importance. They then realize that Maki got ahead of them to pursue Noaya.

After Maki punches Naoya to the ground, Miyo headbutts the cursed spirit. Daido then seizes the opportunity to slash Naoya in half, with Maki kicking his top half away before he can heal himself together. Daido, along with Maki and Miyo then witness as Naoya's human form climbs out of the cursed spirit's lower half and casts Domain Expansion.

Trapped inside Naoya's Time Cell Moon Palace, Daido and Miyo are hit by film strips, but otherwise suffer no effects. Assuming the domain's effect misfired, the two fighters rush towards Naoya. Lacerations suddenly appear on their body that bleed profusely, forcing them to stop in their tracks. It is revealed that Naoya's Domain Expansion allows him to target individual cells with Projection Sorcery's 24 FPS rule, thus disrupting them when a target moves within his domain and dealing damage. Daido pretends to desperately swing his sword at Naoya, only for his hand to be cut off as it flies over Naoya's head with the blade. In fact, he was throwing the Split Soul Katana to Maki, who was behind Naoya and is unaffected by the domain's effects due to her Heavenly Restriction. Maki then singlehandedly exorcises Naoya, freeing the three from the domain, albeit leaving Miyo and Daido severely wounded.