Tesshin, originally named Chibi, is the son of Kurojaki, leader of the Kōga Clan. After his father’s death, he is raised by Gin and nurtured by Moss within the Ōu army. His youth is marked by surviving an assassination attempt by Wilson, a vengeful collie, and a subsequent rescue by Cross, forging his unwavering loyalty to Gin and the Ōu.

As the adult Kōga leader, Tesshin initially declines an alliance with Weed, influenced by the Kōga Elder’s illness. Upon the Elder’s counsel, he pledges support for Weed’s mission to save Gin from Hōgen. In a pivotal encounter, he rejects Gin’s plea for euthanasia, insisting on rescue and relaying vital intel to Weed. He escorts Weed’s injured allies to a restorative hot spring, joins their pack, and mentors Weed in the Zetsu Tenrō Battōga. Though proficient in the technique, he recognizes Weed’s superior mastery, cementing their bond as mentor and student.

In manga canon, Tesshin’s early hostility toward Weed stems from misinformation blaming Ōu for Kurojaki’s death. After uncovering the truth through the Kōga Elder, he allies with Weed, engaging in decisive battles against Hōgen’s forces. He defeats Genba, causing permanent injury, and nearly kills Hōgen before Sniper’s attack leaves him critically wounded. Rescued by Akame and Gin, he recuperates with Moss’s care, reaffirming his Ōu allegiance.

During the Russian Arc, Tesshin operates as a spy against Viktor’s army in Hokkaido. Cornered in a gorge and injured, he later returns to combat post-recovery. His endurance is tested in clashes with Viktor’s forces, enduring severe wounds while fighting alongside Jerome and Lydia.

In *Ginga Densetsu Weed: Orion*, Tesshin survives a volcanic catastrophe, trains youths in Battōga under the alias “Jack of Tochigi,” and safeguards territories from Kurohabaki Masamune’s faction using guerrilla tactics. Injured confronting Masamune, he is saved by Sanada ninja dogs, later reuniting with Weed to strategize against their foe. His leadership proves vital in the final clash, dismantling the enemy’s forces.

In *Ginga: The Last Wars*, Tesshin battles Monsoon’s bear army, suffering life-threatening wounds. Captured and imprisoned, he is named successor by the dying Kurotora, underscoring his esteemed role. He shifts to leading Ōu survivors amid relentless threats.

Personality-wise, Tesshin transforms from a resentful, aggressive youth into a composed and devoted leader. He champions justice, rejects deceit, and balances tradition with pragmatism. His combat style synthesizes Gin’s techniques with Akame’s agility and John’s ferocity, though his Battōga remains surpassed by Weed’s mastery. His journey traces a path from vengeance-driven heir to a tactician and mentor revered across generations.