Souther is the sole successor of the Nanto Hōō Ken ("South Dipper Phoenix Fist) style and one of the Nanto Roku Sei Ken. Souther bears the destiny of the Star of Leadership, also known as Polar Star and Star of the Southern Cross. The Star of Leadership rules over the other five stars of Nanto; therefore, none of the other Nanto successors can defeat him.

Souther establishes himself as Holy Emperor after Raoh's injury and becomes known as a cruel and heartless man, kidnapping children to build his Holy Cross Mausoleum. Souther was once warm and loving child, adopted by the wise master of Nanto Ho-oken, Ogai. However, because of Nanto Ho-oken's awful legacy, Ogai tricked Souther into killing him in order to be surpassed by his student. Souther was devastated by his master's death, and crushed his emotions with hate and cruelty. 

After meeting Shū, Kenshiro fights against Souther and loses horribly when Hokuto Shinken does not work on Souther's body. After Shū's death, he fights Souther again and is able to discover that Souther has dextrocardia situs inversus totalis-- his heart is on his right side and his pressure points' positions are subsequently reversed from where a normal person's would be. He defeats Souther with a merciful "Ujo Mosho Ha", much to his surprise. Despite his tyranny, he is shocked that Kenshiro displayed mercy towards him. He then dies in front of Ogai's shrine, regaining his humanity.

In the movie Raoh Den: Junai no Shou, his death scene is different than in the manga or TV series; there is no reference to his sensei Ogai or the motive behind the pyramid. The moment when he embraces his sifu's body is omitted. Instead, Souther commits suicide by stabbing himself with his fist, refusing to die by Hokuto Shinken.