Soga hails from the Land of Asura with his younger sister Reina, sharing a childhood with Raoh there. Following Raoh, he and Reina leave their homeland to join his conquest across the wasteland. As Raoh's military strategist, Soga employs the swift kicking techniques of Sūzan Senpū Kyaku, driven by a core motivation to unite Raoh with his brothers Toki and Kenshiro for supremacy.

Physical hardship defines Soga's path; escaping Cassandra with Raoh and Reina, he loses his right leg to a trap, replaced by a mechanical prosthetic. Influenced by encounters like Ryuga's, Soga grows ruthless, prioritizing Raoh's ambitions above his own humanity. He sustains a fatal injury battling Gaiya, leaving him only two months to live.

Facing imminent death, Soga orchestrates a deceptive assassination attempt on Raoh. He deliberately sacrifices himself, dying by Raoh's hand, to instill discipline within the complacent army. This calculated strategy is known beforehand to Raoh and the apparent assassin. Soga documents the full truth behind this scheme in a letter intended for Reina, revealing the staged nature of his death and its purpose.

Within "Legend of Raoh: Chapter of Death in Love," Soga features significantly in Raoh's conquests and his complex relationship with Reina. His actions and the letter's revelation impact Reina's understanding of events, contributing to the thematic exploration of loyalty and sacrifice surrounding Raoh's forces.