Mokuren is a member of the Uruha and use to be partnered with Koganei. He was also a member of the Uruha (Maboroshi).
Mokuren is a ruthless and psychopathic killer. He intensely loves to kill women, and even refuses to do so with men, however, he later makes a special exception for Recca, who humiliates him in their "fight". After being so easily defeated, Mokuren swore revenge against Recca, and eventualy comes to hate all the Hokage by association.
He will do whatever it takes to ensure tha he comes out the winner, which includes blatantly lying and limitless cheating. During his fight with Kaoru, he played on his opponents memories of how they got along as partners, tricking Kaoru into turning his back on Mokuren. During his first battle with Tokiya, he promised to let Kaoru go, if Tokiya dropped his sword, but instead played dumb as if he never made any such claim, and continuied to mercilessly assault Tokiya.
After he was defeated by various members of Hokage, he felt that they all looked down on im as if he was less than they were and embarrassed him. Mokuren also believed that all people were selfish, and that no matter what they said, they were always out for themselves in the end.
He is described as being like Mikoto's male counterpart.
from: http://flameofrecca.wikia.com/wiki/Mokuren