Sendai Aka no Ou makes his debut in volume 26 as a happy-go-lucky goofy bookworm hiding in the dungeon to read. He gave Shinrei new hope by asking him for the meaning of a certain phrase, which enlightened Shinrei. He then destroyed the barrier Hishigi set up for Shinrei with ease and set Shinrei free. Shinrei deduces that he is the Sendai Aka no Ou based on the fact that he claims to have sent Kyo out into the world years ago and that he has the power to destroy Hishigi's Taishirou barrier.
The first true display of power comes when the newest Taishirou, Tokito, who is fed up by his goofiness and lack of seriousness, tries to shame him. He reads her mind easily and with just killing ki defeats her without moving. The next fight he has is when Yukimura tries to save Yuya and Sakuya. Even with Yukimura's wits, strength, and abilities, the Sendai Aka no Ou wins in a playful fashion, the only sign of trouble being that his glasses were cut.
Sendai Aka no Ou was of the previous generation of the Mibu. He was once kind and benevolent but became evil, most likely due to his near immortal status, which slowly drove him insane (such as Chinmei, who lost nearly any capability to feel, thus killing to keep his sanity). He foresaw this change in himself and told both Kyo and Shihoudou to kill him should he ever hurt the Mibu Clan. Aka no Ou was the first of the Battle Dolls created by the true Mibu and the first of the Red Cross Knights. His real name is Kyoichiro. Kyoichiro is the father of Kyoshiro, Chinmei, and Kyosaburo, who are all his clones. He is the greatest master of the Mumyou Jinpu Ryuu. He can execute three Suzaku compared to the normal one. He knows all four of the divine gods. His skills are so high that he can summon many god beasts at once. He finally fights against Kyo after the fight against Kyoshiro, and uses several high-level techniques to kill Kyo; at one point, the Former King re-absorbed the bodies and blood of his Red Knights, further increasing his own power with the return of his blood. Even though the Former King became very powerful, Kyo turned into a true demon (due to his sword), and was then thoroughly wounded. He then tries to become a demon god, the destructive form of true Mibu, but Sasuke and Benitora appear holding the Aka no Ou's heart, which has a cross on it. This cross means that the Aka no Ou is not a true Mibu, but instead the First Red Cross Knight, Mibu Kyoichiro; therefore, he cannot become a true Red Eyes demon god, such as Kyo. The Aka no Ou calls back his heart in an attempt end to his own life, destroying the Red Tower as well as himself.
Of the Sendai Aka no Ou, he was portrayed as a great, mysterious, and benevolent King who doted on children and Kyo and even the defects the Mibu clan created. He was shown to be very affable with children, even playing with them, similar to the first Aka no Ou. He also defeated Hotaru easily, and instead of charging him with high treason, he sent Hotaru out to meet Kyo on the pretext of spying on him. He is always shown to be a mysterious dark figure with his face concealed at the start of the manga.
The ageless being Sendai Aka no Ou is ancient beyond imagination. The only other one who is closest to him is Shihoudou, who too is the eldest Taishirou ever. Both of them share a special bond, and the Sendai no Ou made her promise, a promise that he also made with Kyo, to kill him when he became evil. However, Shihoudou reveres and loves the Sendai Aka no Ou could not bring herself to do it at first.
It is not clear when the change in Sendai no Ou truly began, but he reveals that it started because he gradually grew disgusted with the inherent flaws in human nature, especially the human love of violence. He had already foreseen himself becoming evil; therefore, he made a pact with Shihoudou and Kyo to kill him. He also cried blood, much like Chinmei, an allusion to the idea that both men had lost so much (literally and emotionally) that there was nothing left inside spiritually. A scene around the same time when Kyo was young also showed the Taishirous, including Muramasa, begging the Sendai Aka no Ou to save the race from the terminal disease which would eventually exterminate all of them.
Vova
