Sekiou is a madogu wielder and a murderer who was sentenced to prison for 200 years but, now works for Kurei.

After being initially defeated by Domon, Kurei decapitates him and presents his head to the Hokage. He is also the younger brother of Gaō, who eventually seeks revenge for his brother's death.

from: http://flameofrecca.wikia.com/wiki/Sekiou