Keizo Arashi/Synopsis

History
Before creating Black Dragon alongside Wakasa Imaushi, Takeomi Akashi, and Shinichiro Sano, Benkei used to be the leader of Ragnarok, the gang that controlled Kanto’s western side. He was proclaimed as the man named "Redcliff" who stirred a dilemma with Kanto's eastern gang Kodo Rengo that was formerly led by Wakasa. Eventually, their gangs were united by Shinichiro and Benkei joined his team to devote himself in creating the largest gang in Japan alongside his friends. Once the First Generation Black Dragon was disbanded, Benkei worked at a gym with Wakasa until the formation of Brahman.

Three Deities Arc
As Shion Madarame threatens Senju Kawaragi and gloats his former authority over the Ninth Generation Black Dragon upon Rokuhara Tandai clashing with Brahman to earn Takemichi Hanagaki's allegiance to their gangs, Benkei knocks him off his feet out of annoyance, deprecating his vicious leadership as a former well-respected Black Dragon Captain and founding member. Afterward, he tells Senju to drop the fight as Brahman only collided with Rokuhara Tandai to recruit Takemichi, their main objective, but gets attacked by Kakucho Hitto who defeats him with just one hit.

A month later on Tanabata, Benkei gathers Brahman members to the amusement park with the objective of brawling with Rokuhara Tandai who recently killed Ken Ryuguji. Alongside Wakasa Imaushi, he runs off to fight South Terano as the war begins upon the arrival of all three gangs who equally control Tokyo, including the Kanto Manji Gang. Before South lands a punch on Takeomi Akashi, Benkei blocks his movements and ridicules his strength. Together with Wakasa, they take down a hundred of Rokuhara Tandai's men until they come face-to-face with South. Watching from the sidelines, Senju explains Benkei's origin to Takemichi. Prior to joining Brahman and Black Dragon, Benkei was the fearsome leader of Ragnarok, a delinquent gang comprising of over six hundred members that once controlled West Kanto. He was the so-called man who walked through the aftermaths of a bloody battle drenched in blood from head to toe and was nicknamed as "Redcliff." Ragnarok was said to be rivals with the eastern gang Kodo Rengo, formerly under the command of Wakasa, until their gangs were unified by Shinichiro Sano, the founder of and the man who eventually became their boss in Black Dragon. For this reason, Takeomi believes that the toughest fighters in Japan are undoubtedly the both of them.

Back to the fight, Benkei launches South to the ground with an unexpected hit. South seemingly loses, but he rises back up on his feet and erupts a mayhem. His dark impulses strengthen and he manages to mercilessly beat Benkei up and heavily damage his face, preventing him to fight any further. Seeing his and Brahman's defeated state, Senju incites a fight against South on her gang's behalf.

In a series of flashbacks by Takeomi during the war between the Three Deities, Benkei is briefly seen in his visions. Later on, Benkei appears in another flashback where he applauds Senju's extraordinary strength and power after hearing her desire to create a gang of her own.