Oodenta Mitsuyo is a tachi said to have been forged by the swordsmith Miike-Denta Mitsuyo and one of the Tenka Goken, the five greatest swords of Japan. In the anime Zoku Touken Ranbu: Hanamaru, he appears as a sword warrior who is manifested at the citadel alongside Sohayanotsuruki. Historically, the blade was worked in a style so different from other swords of its time that it was regarded as a spiritual sword with the power to heal illness when placed at a sick person's bedside. His spiritual power is said to be so strong that even small birds and animals would not come near him, and the real sword was kept carefully sealed in a storehouse, which has made Oodenta known in the story as a genuine stored-away son.

In appearance, Oodenta is tall and lean, with long, unkempt dark hair and red eyes, and he dresses mostly in black with a red cord across his chest, a detail often read as a symbol of his former sealing. His fierce and imposing look contrasts sharply with how he behaves. He tends to speak in a low, mumbling voice and carries himself with a quiet, subdued manner. Among the Tenka Goken, he is commonly understood as the one with a melancholic and negative outlook. Long years of confinement have left him convinced that he is not meant to be used as a weapon, and that his only purpose is to be brought out when someone falls ill. He believes that people and animals are afraid to touch him or stay near him, and this belief has made him withdrawn, lonely, and resigned to his fate rather than angry or bitter.

His main motivation in the story is to find a place where he can belong despite the isolation his power creates. He avoids the other residents partly out of consideration, because he does not want his spiritual energy to frighten the animals living in the citadel, and partly because he has internalized the idea that he belongs locked away. As a result, he chooses to spend time alone in a separate room. His personal arc is about being drawn out of that self-imposed seclusion and learning that being feared by animals does not mean he must also keep his distance from people.

Within the story, Oodenta is brought into the citadel by the near-sword attendant Yamabagiri Kunihiro, who manifests both him and Sohayanotsuruki. Yamabagiri's attention initially falls more on the bright and cheerful Sohaya, which highlights Oodenta's quieter presence. The most significant relationship in the anime is with Sohayanotsuruki, who is attributed to the same smith and is regarded as his fellow blade from the Miike school; the two are often treated as brothers, and their temperaments are direct opposites, with Sohaya's openness and optimism standing against Oodenta's gloom. Another important connection is with Maeda Toshiro, the young sword warrior who brings meals to his room and worries that Oodenta should live together with everyone else. This pairing carries a fitting historical echo, since the real Oodenta Mitsuyo is famous for its healing legend tied to the Maeda family, and in the source material the two characters also share a special recollection event when they fight together.

Over the course of his appearances, Oodenta develops from a resigned and self-isolating figure into someone who begins to accept a role alongside the others. The care shown by Maeda Toshiro and the acceptance of the citadel community gradually persuade him that he does not have to return to the storehouse, and that even a sword feared by illness and animals can live among companions.

His notable abilities center on his overwhelming spiritual power, which is strong enough to ward off sickness and misfortune and so intense that animals flee from him. This power is both a gift and a burden, because it feeds his feeling of being untouchable. In combat, he fights as a tachi with great strength and endurance, and among the Tenka Goken he is characterized as an offense-oriented, heavy-hitting type. He does not enjoy fighting, but he accepts it when the situation demands, since he has no wish to be sealed away again.