Yousuke Otoha is a character dark in history and actions, breaking the traditional mold of a Japanese hero. He is portrayed as the product of incest between his mother and his brother who is the local yakuza boss. Otoha's back-story states him as suffering from congenital insensitivity to pain which lends the character a merciless reputation as his brother's enforcer.

Suffering from post-traumatic amnesia, Otoha has accepted the role of protector of Tokyo, the role of Karas, to to defend its inhabitants and the youkai from Eko and his Mikura. With his pocket-watch device (no explanations on that through the series), Otoha can transform into different forms. He can take on the form of "Hishokaku" to fly, or a ninja-like form to fight. As Karas, Otoha is the last bastion of defense against Eko. In his free time, Otoha helping to run a hospital for youkai.

(Source: Wikipedia)