Cousin of Hakufu and a tough fighter in his own right.
Hakufu Sonsaku's rich cousin and an attractive pretty boy; both Kanu Unchou and Ukitsu have expressed exclusive interest in him. Although only a C-rank, his lack of confidence and his short resume of victories (or battles for that matter) keep him from becoming A-ranked despite already having the power of one. He has a crush on his cousin Hakufu and is generally shy and well-meaning, making life very difficult for him. Oddly, Hakufu doesn't seem to mind being naked around him, showing how much she trusts him. But at times she thinks he is a pervert whenever he is caught in an embarrassing situation (such as Hakufu catching him staring at her). He showed some great power when he defended Hakufu and Kakouton from the Ugan gang (astonishing even Kakouton). He stayed behind to fight and eventually was captured, allowing the other two to escape. While being held captive in Kyosho, he was seduced by three beautiful girls (one of them being Seito's spy, Shoukan, who reveals her identity to him afterwards) in an attempt to make Koukin betray Nanyo and fight for Sousou Moutoku. Although he resisted, Gakushin is now using her powers on him to learn the location of one of the Hyakuhekitou. He is now considered to be one of the Four Devas of Nanyo, taking Kannei's place.
Mostly the same, he is still a well-meaning young man who is attracted to his cousin (though the sexuality of it is toned down) but has yet to demonstrate his considerable power and serves even more so for comic relief than in the manga. He is the only character whose after-episode biography in the first season poked fun at him, saying that after he got lost in a forest Hakufu nicknamed him "The Lost Koukin-chan". As a child he was called "Crybaby Koukin" by other children, because he always cried when others bullied him. Hakufu was usually there to protect him from bullies. Koukin was unable to stop Hakufu's dragon when she fought Ukitsu; instead he got pummeled half to death in the attempt only to have Hakufu stop her dragon on her own. After hearing of Hakufu's demise, he blames Koumei for manipulating the events that led to Hakufu's fight with Sousou. However, Kanu proved to him that it was Hakufu's choice to challenge Sousou, and her fight with Kanu was one out of respect as toushi and not out of hatred. This leads to Nanyo and Seito forming an alliance to face Kyosho. He is now considered to be one of the Four Devas of Nanyo, taking Kannei's place. He returns to being a student after the Battle of Chibi.
Ikki Tousen: Shūgaku Tōshi Keppu-roku
Ikki Tousen's OVA movie taking place after Xtreme Xecutor.