Hajime Tsukishima was born on Sado Island, ostracized by locals as the "murderer's son" due to his father's reputation. His sole childhood friend was a girl nicknamed Igogusa, known for her unruly hair; she was the only person who used his given name. As a young adult, he enlisted in the Shibata-based 2nd Division and fought in the First Sino-Japanese War. Before departing, he promised Igogusa they would marry and leave Sado together upon his return. When letters from Igogusa stopped near the war's end, Tsukishima returned home to find false rumors of his death circulating. Discovering her shoes on the shore led him to believe she had committed suicide. Tracing these rumors to his father, he killed him in a rage before learning the reason, resulting in his imprisonment and a death sentence for parricide. While incarcerated, First Lieutenant Tokushirou Tsurumi visited him. After hearing Tsukishima's story, Tsurumi investigated and falsely claimed Igogusa was still alive, presenting a lock of her hair as proof. Tsurumi secured Tsukishima's pardon by recruiting him into the 7th Division, assigning him to learn Russian alongside Hyakunosuke Ogata. Tsukishima subsequently participated in military operations, including the 1902 kidnapping of Otonoshin Koito at Fort Goryokaku and the Siege of Port Arthur during the Russo-Japanese War. During the 1905 Battle of Mukden, a soldier from Sado informed Tsukishima that Igogusa's remains had been found beneath his father's house. Confronting Tsurumi about the nine-year deception, Tsukishima attacked him but shielded him from artillery fire during the bombardment, sustaining a significant abdominal scar. Wounded and disillusioned, he pledged his remaining life to Tsurumi's service in exchange for this perceived lifesaving act. Tsukishima serves as a sergeant in the 7th Division. He maintains a stoic, serious, and efficient demeanor, often acting as the straight man to eccentric comrades and superiors like Tsurumi and Otonoshin Koito. Despite recognizing Tsurumi's manipulations, he exhibits unwavering loyalty, rooted in Tsurumi saving him from execution and giving his life purpose. He perceives his own life as having minimal inherent value, feeling too deeply committed to Tsurumi's cause to turn back. This loyalty manifests in brutal efficiency during missions; he follows orders dutifully, including the cold-blooded murder of Captain Wada on Tsurumi's command during the Escape King Arc. While generally reserved, he demonstrates concern for comrades, such as consoling Genjirou Tanigaki or guarding the injured Kouhei Nikaidou. His internal conflict surfaces in moments like discarding Igogusa's lock of hair into the sea after learning the full extent of Tsurumi's deceit, reflecting resignation and entrapment. Physically, Tsukishima is short but muscular, with a buzz cut, dark eyes possessing a slight green tint, stubble on his chin, and two distinctive lines under his eyes. His nose is short and flat, inherited from his mother. He bears a scar on his abdomen from the Mukden explosion. He typically wears the standard Imperial Japanese Army uniform of the 7th Division, often with a hooded coat. His notable abilities include significant physical strength and endurance, proficiency in hand-to-hand combat (favoring powerful kicks), skilled marksmanship with his standard-issue Arisaka Type 30 rifle, and functional fluency in Russian, though not for complex translations. His involvement in the division's quest for Ainu gold spans multiple key arcs. In the Edogai Arc, he participated in staking out a grave in Yubari to catch a skin thief. He later guarded Yasaku Edogai's taxidermy shop. After a confrontation involving Sugimoto, Shiraishi, and Ogata, he rescued Edogai, leading to a chaotic mine cart chase and explosion. Edogai perished with crushed legs, entrusting Tsukishima with fake tattooed skins and a final message for Tsurumi, which Tsukishima delivered. During the Con Artists Arc, he cared for the severely wounded Nikaidou. Throughout these missions, his role evolved from initial awareness of Tsurumi's manipulations to deeper complicity and acceptance of morally questionable actions in service of Tsurumi's goals. His loyalty persisted even as he witnessed the increasing brutality and moral compromises of the division's campaign.