Oshtor originated from a low-ranking Yamato noble family. Leaving his hometown to become a soldier, he rose to prominence through deeds that captured the Mikado's attention, eventually becoming Imperial General of the Right. His leadership and loyalty earned public trust, though he frequently used the alias "Ukon" for informal interactions, as his true identity created distance. This dual life reflected an internal conflict: the formal, duty-bound Oshtor persona contrasted with the relaxed Ukon identity he subconsciously favored. His background prior to becoming a general is explored in *Monochrome Mobius*. Oshtor journeyed with Shunya, who claimed to be the daughter of his father, Pashpakur. They traveled to Arva Shulan, encountering allies including Munechika and the mechanical doll Halu. During this time, Oshtor was less mature, frequently quarreling with Mikazuchi and displaying insecurity. His transformation into a disciplined leader occurred after receiving the Aruturuka mask during conflict with Arva Shulan's forces. Following the defeat of the antagonist Mayacowl alongside Mikazuchi, both were appointed Imperial Generals and tasked with protecting the Mikado's daughter, Anju. Key relationships defined Oshtor: - Shunya, his adoptive sister, shared a familial bond, though she harbored unreciprocated romantic feelings. - Mikazuchi served as both rival and trusted comrade; their dynamic evolved into the "Twin Shields of Yamato." - Nekone, his younger sister, received his deep affection despite his tendency to tease her. - Haku, befriended under the Ukon alias, became a protégé. Noticing Haku's success impersonating him during a prank, Oshtor devised a plan for Haku to serve as his body double. Oshtor died during the Yamatan Civil War. Framed for the Mikado's assassination and Anju's poisoning, he was imprisoned but rescued by Haku and allies. Fleeing with Anju, he confronted Vurai, who believed him guilty. During their battle, Nekone's intervention distracted Oshtor, enabling Vurai to land a fatal blow. With his final act, Oshtor defeated Vurai and entrusted Haku with his mask and legacy—to protect Anju and uphold Yamato's stability. After his death, Haku assumed Oshtor's identity using the Akuruka mask. The mask fused with him, altering his appearance, voice, and demeanor to match Oshtor's permanently. As "Oshtor," Haku led the Ennakamuy faction, suppressing his original personality and relationships to maintain the ruse, including distancing himself from Kuon, causing her distress. Posthumously, Oshtor appeared in the afterlife during *Mask of Truth*'s climax. Alongside another fallen comrade, he convinced the temporarily deceased Haku to return to the living world, granting him Hakuowlo's mask to facilitate revival, reinforcing Oshtor's enduring commitment to Yamato's protection beyond death. In the *Lost Frag* spin-off, alternate versions feature: - Marebito Oshtor, primarily living as Ukon while working as an arbiter, his masked self operating anonymously. - A younger version from *Monochrome Mobius* appearing in Tamamikyo. - Fugito, identified as the former Owlo of Kunashikor.