Hailing from Hagakure village among the Shadow Warrior clans, Ryoma Kogure bears a sacred halberd—one of three mystical Demon Blades prophesied to vanquish the demonic forces endangering Sengoku Japan. This weapon is also known as the Spear of Sorcery. Ryoma possesses a headstrong nature and a powerful moral compass.

He witnesses his father Genyusai fall during a demon invasion orchestrated by Oboro ninja Jinnai Saegusa. Genyusai compels Ryoma to abandon him and prioritize their mission, forcing Ryoma to sacrifice familial loyalty for duty. Tragedy compounds when Jinnai later kills Ryoma's younger sister Kikyo; she perishes in ally Ayame's arms after shielding Ayame from Jinnai's attack. Kikyo's death fuels Ryoma's determination against their foes.

Ryoma develops unrequited feelings for Kayo Momochi, a Koga representative and sister to Iga leader Tanba Momochi. Possessed by Oboro ninja Masago, Kayo is driven to murder her comrades and her own brother. Ultimately, to end the possession and prevent further slaughter, Ryoma fulfills Kayo's desperate request and kills her.

During the final clash against Oda Nobunaga and demon Ranmaru Mori, Ryoma suffers grave wounds from Oboro ninja Kagami. He defeats her but succumbs to his injuries, his final thoughts fixed on Kikyo. Ryoma meets his end alongside Sakon Hayate at Azuchi Castle. Their sacrifice ensures Ayame can fulfill the prophecy and defeat the demonic threat.