Myōjin Yahiko (明神 弥彦 Myōjin Yahiko?), known as Yahiko Myojin in the English-language dub. Yahiko is an orphan from a samurai family and was forced to work as a thief to repay the debt that he had supposedly owed due to his parents death before they could pay it back. When he is rescued by the main character of the story Himura Kenshin and decides that he would grow up to be just like Kenshin but due to his strong beliefs in not teaching anyone else the sword style he had obtained, he enlisted Yahiko to be trained by Kamiya Kaoru, the teacher of the Kamiya Kasshin-Ryū. As the series progressess, Yahiko becomes skilled at the swordmanship and comes to face many opponents.
A hotheaded child, Yahiko is arrogant, cheeky, a user of profanity, and bad-mannered; and he already bestowed upon himself the title 'Tokyo Samurai' since his father was a samurai and died during the Battle of Ueno during the Boshin War, slain at the Keneiji Temple. As the years go by, Yahiko learns the principles of Kamiya Kasshin-Ryū, which coincides with Kenshin's ideals. Even though he overrates himself, Yahiko defeats several enemies - even one of the Ten Swords.
In time Yahiko becomes a master swordsman, whose skills are nearly equal to Kenshin's. He also becomes an assistant master of the Kamiya Kasshin-Ryū dojo, which prospers again. On the day of his fifteenth birthday, after battling Kenshin in a one-strike match, Kenshin gives him the Sakabatō. By this time, he has grown into a level-headed, contemplative, and caring young man.
Yahiko has a friend/rival, Tsukayama Yutarō, who is a rich boy tricked into believing his sensei, Isurugi Raijūta, cared about him. Yutarō was a brief student of the Kamiya dojo after he revealed that he was never trained by Raijuta (in the anime, he was quickly defeated by Yahiko, while in the manga, the battle was halted as Yutaro could not hold his shinai properly).
Yutaro, however, was hit by Raijūta's Tobi Izuna (a huge gust of wind from an overhead swing that can kill someone) in his right arm and his nerves were damaged so he could never use a sword again. Yutarō moved with his uncle to Germany so that his uncle could seek treatment for his arm, thus allowing Yutarō to one day use that arm again. Before he left, Yahiko swung his bamboo sword at him and he blocked with his walking cane and said "Even without my other arm, I can still use a sword" and promised that he will return to Tokyo to challenge Yahiko. At the end of the series, Yutaro and Yahiko are the Acting Instructors of Kamiya Kasshin-Ryu.
He has a sweetheart, Sanjō Tsubame, who works at Akabeko (a restaurant where Yahiko also works) as a waitress.
Yahiko is trained in the series in the Kamiya Kasshin-Ryū swordsmanship style. During his six months of training his teacher, Kamiya Kaoru, recognizes him as the strongest child in Japan, though Yahiko commonly says that is not enough since he wants to be as strong as Himura Kenshin. After seeing several of his fights, Yahiko becomes adept in imitating some of Kenshin's Hiten Mitsurugi-Ryū (飛天御剣流? lit. "Flying Heaven Honorable Sword Style") techniques and combining them to perform many other powerful sword techniques.
During the Jinchu Arc, since Yahiko wants to become strong enough to protect his friends that he is taught the Kamiya Kasshin-Ryū's two succession techniques. In the first one, Hadome, Yahiko crosses his arms over his head and catches the blade of the opponent with the back of their hands. This allows him to maintain their grip on their sword while catching the opponents blade at the same time. However, if properly used, it can be chained into Hawatari Kamiya Kasshin-Ryū's offensive succession technique. It is a counter-attack and can only be performed after a successful use of the Hadome technique. From the Hadome position, Yahiko twists his wrists, thusly stripping the weapon of their attacker away from their wrists. He successfully learns both of this techniques and becomes so adept at using the Hadome, that Yahiko starts performing variations of the technique, even becoming famous when he is a teenager due to his title of " the man who has caught 1000 blades".