Birth date: March 18
Blood type: B
Birthplace: Setagaya-ku, Tokyo
Born Manabu of the Ryuuzu Noble House, Tendou is a man with superhuman abilities who is able to transform humans into ogres and demons using the Dark Arts. He has a selfish, wicked sense of justice, but he isn't entirely evil; Tendou is often shown in a sympathetic light.
SpoilerIt is revealed that his mother was a descendant of the rogue Kodzunu clan, which revolted during the Bakumatsu when the Shogunate used force to take a girl with the Bodhisattva Eye from their family. Their clan ultimately lost and went into hiding.
In modern time, when it was discovered by the Ryuuzu household that Tendou's mother was a descendant of the Kodzunu clan, his father's family locked her away, leading to Tendou developing a strong Oedipus complex. When Tendou (still Manabu) was fifteen, his mother committed suicide by hanging herself, and visions of her death still haunt him. Wanting revenge for his mother's unfair suffering, Tendou took an offer from a mysterious man named Munetaka Yagyuu, who granted him power. He then slaughtered the Ryuuzu family, and gave up his identity as Manabu.
To avenge his mother, he set out to destroy everything by resurrecting the Kodzunu Kidou-shu (Demonical Horde) and gathering the 10 Sacred Treasures. His ultimate goal, however, is finding the Bodhisattva Eye...
He is often seen with Marie Claire as both work for Yagyuu in causing chaos to disrupt the Dragon Stream, although Tendou openly states he only does what he pleases; he does not care for Yagyuu, which causes much bickering between Claire and himself. Tendou especially grows a strong hatred for Tatsuma Hiyuu, blaming his family for the destruction of the Kodzunu clan during the Edo period, and thus the death of his mother.
The biggest discrepancy between the anime and original video game version of this character is the visual design, although his personality and reasons are inevitably different, as well. Tendou is a descendant of Tenkai Kodzunu from the prequel game Tokyo Majin Gakuen: Gehouchou.
(Source: Wikipedia, original video game data)