Yahiko Myōjin hails from a samurai family. His father died fighting for the pro-bakufu Shōgitai during the Battle of Ueno, leaving his parents financially struggling. After his mother succumbed to illness contracted while working in a brothel, he was orphaned. The Tanishi yakuza manipulated him into pickpocketing to repay fabricated debts tied to her medical expenses. This period bred resentment towards charity and honed exceptional sleight-of-hand skills, though he despised this criminal past. His life shifted when Himura Kenshin intercepted a theft attempt, recognized Yahiko's pride and potential, and freed him from the yakuza. Kenshin arranged for Yahiko to train at the Kamiya Kasshin-ryū dojo under Kamiya Kaoru. Initially brash and dismissive of Kaoru's instruction, Yahiko prioritized learning Kenshin's Hiten Mitsurugi-ryū style. He gradually embraced the Kamiya Kasshin-ryū principle of protecting life without killing. His dedication to kenjutsu intensified, fueled by a desire to embody samurai honor and defend others independently. During the Kyoto conflict with Shishio Makoto, Yahiko accompanied Kaoru to aid Kenshin. He helped defend the Oniwabanshū's Aoi-ya base against Shishio's forces and defeated the Jūppongatana member Henya by adapting Kenshin's Ryūtsuisen technique with a shinai, showcasing rapid growth and tactical ingenuity. After Kyoto, Yahiko confronted challenges during Yukishiro Enishi's revenge plot. He mastered advanced Kamiya Kasshin-ryū techniques—Hadome (blade-catching) and Hawatari (counterstriking)—to defeat Enishi's ally, Otowa Hyōko. Despite setbacks, including injuries from confronting Kujiranami Hyōgo, his resolve solidified. Five years later, he served as acting instructor at the Kamiya dojo. Kenshin formally acknowledged his maturity by gifting him the Sakabatō after Yahiko landed a hit in a spar, symbolizing his transition into a master swordsman. As an adult, he earned renown as "The Catcher of a Thousand Blades," adopting a dark blue haori featuring the kanji for "evil" (aku) as a tribute to Sagara Sanosuke, and carrying both a shinai and the Sakabatō. Yahiko's relationships evolved significantly. His initial rivalry with fellow young swordsman Tsukayama Yutarō matured into mutual respect after Yahiko encouraged Yutarō's recovery from a career-threatening injury. Sanjō Tsubame, whom he met working at the Akabeko restaurant, became cherished; their bond deepened into romance, with Yahiko displaying jealousy when Yutarō flirted with her. His dynamic with Kaoru shifted from contempt to sibling-like camaraderie, while Kenshin remained his primary mentor and inspiration. In later continuities like OVAs and live-action adaptations, Yahiko's legacy as the inheritor of Kenshin's ideals is emphasized. He upheld the vow against killing while teaching Kamiya Kasshin-ryū, reflecting his commitment to protecting the peaceful era Kenshin fought for.