Woverine adopted Amiko in Japan after her mother died. He left her with Mariko Yashida who promised to care for the child. After Mariko died, Wolverine entrusted Amiko to Yukio who raised her as her own and trained her in the martial arts.
When Lady Deathstrike crippled Yukio, Sabertooth kidnapped Amiko and nearly killed her while taunting Wolverine. She was brought back to full health by the Weapon X program and returned to Wolverine as a show of good faith.