Hyakunosuke Ogata is a complex figure defined by his exceptional skill as a sniper and a deeply personal, often inscrutable code of conduct. A former Superior Private of the 7th Division of the Imperial Japanese Army, Ogata is a man who operates with a chilling level of self-possession, loyal only to his own objectives and driven by reasons he keeps hidden from everyone around him.

His background is central to understanding his character. Ogata is the illegitimate son of Lieutenant General Koujirou Hanazawa, a high-ranking commander, and his geisha mistress, Tome Ogata. Raised primarily by his grandmother in Ibaraki Prefecture, his childhood was marked by a lack of parental affection, a void he believes shaped his inability to feel guilt. This upbringing forged a cynical worldview, where he came to view patricide as a rite of passage into adulthood. This personal philosophy culminated in the killing of his own half-brother, Yuusaku Hanazawa. Yuusaku was the legitimate son of their father, a morally upright and popular second lieutenant whom Ogata shot from behind during the Battle of Port Arthur. This act, committed against the orders of his superior, Lieutenant Tokushirou Tsurumi, stemmed from Ogata's inability to comprehend his brother's genuine empathy and lack of killer instinct, which he perceived as a personal affront.

On the surface, Ogata can appear amiable and polite, but this is merely a tool for deception. His true personality is analytical and cold-blooded, a trait befitting a proud sniper who views situations from a distance to calculate the most efficient advantage. He is ruthless and does not hesitate to kill, yet he is not wantonly violent, preferring to escape a losing battle rather than engage impulsively. He is prone to caustic remarks, often mocking perceived absurdity or incompetence, particularly regarding military matters. Despite his general emotional detachment, Ogata possesses a significant amount of pride; he dislikes being doubted and will take on challenges simply to prove a point.

In the story, Ogata serves as a persistent and unpredictable wildcard. He first appears as an enemy to the protagonist, Saichi Sugimoto, and the Ainu girl Asirpa, killing a prisoner they were interrogating. While initially a loyal soldier under Lieutenant Tsurumi, Ogata secretly plots to betray him and seize the Ainu gold for himself, forming a conspiracy with other disaffected members of the 7th Division. After his betrayal is exposed, he drifts between factions, briefly allying with Hijikata Toshizou’s group before becoming a central figure in Kiroranke’s party, with whom he travels to Karafuto. His role is often that of an instigator and a threat, using his sniper skills to drastically alter the balance of power, such as when he executes a double headshot that seemingly kills Sugimoto and another character, forcing Asirpa to flee with him and Kiroranke.

His key relationships are fraught with tension and violence. His dynamic with Lieutenant Tsurumi is one of mutual manipulation, with Ogata ultimately choosing his own path over blind loyalty. His rivalry with Sugimoto is intense and physical, marked by a brutal first encounter that leaves both men with severe injuries. His relationship with Asirpa is perhaps his most complex; he serves as her captor and claims to want to protect her, but he also reveals himself as the killer of her father, Wilk, in a twisted attempt to force her to confront his nihilistic worldview that all people are remorseless killers at heart.

Throughout the narrative, Ogata shows subtle but significant signs of development. Although he maintains his emotionless facade, he is haunted by hallucinations of his slain brother, Yuusaku, suggesting suppressed guilt and psychological turmoil. His confrontation with the Russian sniper Vasily pushes his skills to their limit, costing him his right eye but reaffirming his tactical genius. His personal philosophy is repeatedly challenged, most notably by Asirpa, whose refusal to kill him despite being given every reason contradicts his fundamental belief about human nature. This encounter forces him to confront the possibility that his worldview might be flawed, leaving him defeated not by a bullet, but by an idea he cannot accept.

His notable abilities are almost entirely centered on his marksmanship. Ogata is a prodigious sniper who honed his skills from childhood. He favors the Type 30 rifle for its long-distance accuracy and can make seemingly impossible shots, such as piercing a skull from hundreds of meters away. He possesses incredible mental fortitude, allowing him to remain perfectly still for hours in harsh conditions to fool his opponents. He also has acute hearing, capable of identifying a rifle just by its gunshot, and can speak Russian, a skill he keeps largely hidden.