A Shugoki of immense strength, Okuma was an old friend of The Orochi and helped free him/her from prison. He helps defend the city and drive out the Vikings. After Ayu is captured and left in the swamp, Okuma manages to find her. He was among the soldiers waiting outside the palace to overthrow Seijuro. Once this is done, he joins the armies in the siege on the Blackstone Legion's castle. He opens the gate to Apollyon and lets The Orochi through to reach her.
Okuma was a man of few words. When he did speak it was usually to speak his mind and he speaks in a composed tone of voice. When he does have to speak in other scenarios he tries to use as few words as possible though this appears to be out of awkwardness; such as when he approaches Ayu to tell her about the Vikings escaping, he gives an awkward pause before simply stating 'Vikings'.
- In Japanese, Okuma written in Kanji as 大熊 (Ōkuma), it means "Great Bear", fitting his image as a large Shugoki.