Kuina is a thirty-two-year-old man who leads the Dragon Knight Squad from the dimension La’cryma and is the sole member of that unit to remain in his home timespace. His name translates to “rail” in Japanese. The decay of his physical body forced him to rely on mechanical prosthetics, including a face mask that initially covers an eye and later obscures most of his head, giving him a partially robotic appearance. As the Dragon Knight commander, he would logically possess at least one spin weapon, although none is explicitly shown in the series.

Personality-wise, Kuina is driven by a grim pragmatism and an obsessive, desperate determination. Having concluded that La’cryma is a lost cause, he secretly allies himself with the entity Noein in exchange for passage into the idealized dimension Shangri-La. When Noein breaks this pact, citing Haruka’s growing power and the disintegration of Kuina’s own body as justification, Kuina’s desperation slides into an unyielding fixation. He seizes Haruka and attempts to force Noein to honor the deal. This obsessive drive ultimately proves self-destructive: his body is rejected by the timespace and he disintegrates.

Kuina’s key relationships revolve around his unrequited romantic feelings for his subordinate Kosagi, who does not return his affections, and his transactional, ultimately betrayed connection to Noein. His interactions with Haruka are entirely instrumental, viewing her solely as leverage to reach Shangri-La. Over the course of the story, Kuina evolves from a seemingly authoritative leader into a broken figure consumed by a doomed bargain, and his physical decay mirrors the collapse of his ambitions. His arc is defined by the ruthless choices he makes in the face of a dying world, culminating in his erasure when the very forces he sought to exploit turn against him.