Sekimei

Sekimei is an Oni that was sealed by the first Houjou Souun. He was released by Keikoku in the events of the Ran Route in Sengoku Rance, and serves as the final boss.

About
The strongest of the Oni that served the Houjou Souun of the first generation. As Souun recognized its power, he himself made sure that after his death Sekimei was sealed with his remains. So far, the only person who could control that power is said to be the first Houjou Souun.

Trivia

 * Sekimei is the only final boss in Sengoku Rance that isn't Xavier