Suzu Asahina shares an intense, inseparable bond with her twin brother Ryo Asahina, together forming the dual entity called the Platonic Twins. They constantly sense each other's presence, location, and emotions. Facing death in a mountain blizzard, Ryo accepted a Kaiser Stone from Master Ohga to save Suzu, creating their merged combat form. In this fused state, identified as a Suspicious-Looking White Giant, Suzu forms the central torso, her limbs augmenting Ryo's body structure, and she occasionally attacks independently with her arms during battles. Suzu loves Ryo deeply, considering him as vital as air, and draws strength from their connection. While generally aligned with Ryo in purpose, she exhibits slightly more vicious tendencies during confrontations. Their loyalty to Ohga is absolute, serving as his guards and challenging intruders at his command.

A pivotal moment occurs when Ryo sacrifices himself to shield Suzu from an attack by Gowcaizer (Isato Kaiza). Devastated by Ryo's death and swearing vengeance, Suzu demands a Kaiser Stone from Ohga. Warned of the dangers—as their power was designed for shared use—she persists. Ohga implants the stone into her chest, transforming her into the solitary and unstable entity Platonic Slave, consumed by rage.

During Ohga's tower invasion, Suzu confronts Isato and Kash Gyustan (Hellstinger) as Platonic Slave. She focuses her assault on Isato, who refuses to retaliate and endures her blows. When her fury culminates in a final strike, she breaks down upon realizing her inability to commit murder. The Kaiser Stone then begins to painfully reject her, threatening her life. Kash intervenes, using his own stone to neutralize the corruption in hers, saving Suzu. Post-redemption, she survives, freed from the stone's influence and her vengeful path.