Hasegawa Ashitarō is a resident student of the Kamiya Dōjō in the 16th year of the Meiji period. Not much is known about his past except that he served Shishio Makoto and the Juppongatana before finding his way to the dōjō. He is the current master of Shishio's signature weapon Mugenjin.
Ashitarō has a very unkempt appearance compared to the other residents of the Kamiya dōjō. His brown hair is wild and ear length, his clothes appear dirty and ragged. His eyes are a brilliant purple hue, and he appears to have red tattoos around the base of his eyes. His base cloths consist a simple black gi and pants. He wears arm guards on both arms and sandals with foot wraps on his feet. Over this he wears a red and white robe in a similar fashion to his former master Shishio Makoto.
Ashitarō appears to have a fairly "no non-sense" personality. When prompted to lie about the prices listed on the brothel poster for Kubota Asahi, Ashitarō frustratingly proclaimed that it said whatever she claimed it did. This is due in part to Ashitarō being illiterate; claiming that reading "didn't put food in his belly".
Ashitarō is prone to getting into fights, and when doing so seems to lose himself in the moment. After starting a fight to defend Kubota Asahi at the Akabeko, Ashitarō ended up fighting with the police as well. It was commented the he forgot who he was fighting. This effect becomes even more apparent when Himura Kenshin intervenes to try and calm him down. This intervention has much the opposite effect causing Ashitarō to swing into a blind rage. In this mindset Ashitarō is able to effortlessly utilize techniques from the Three Secret Swords style created by Shishio Makoto, specifically First Secret Sword: Blazing Soul. After recovering from his outburst he appears remorseful, however this is short lived as he almost immediately gets into a minor argument with Alan.
Like other members of the dōjō, he is quick to complain when hungry.
- Himura Kenshin - Ashitarō appears to revere Kenshin to some degree. It is unknown exactly how much Ashitarō knows about Kenshin's past. While he does not refer to Kenshin as his current master, when Kenshin set the ultimatum that Ashitarō will not draw Mugenjin from its sheath again until instructed, he appears to comply.
- Kubota Asahi - Ashitarō appears to have some history with Asahi, mentioning that she once gave him food. She is taken aback that he remembers this small gesture. Later when Asahi is being gas-lighted by the owner of the brothel she is indebted to, Ashitarō sides with Asahi during the argument. This causes a fight to break out at the Akabeko.
- Inoue Alan - Ashitarō appears to have a very argumentative relationship with fellow dōjō resident Alan. Alan seems to often respond to Ashitarō with quips that cause the latter to comically lash out at him.
- Shishio Makoto - It is known that Ashitarō was part of Shishio's plot to conquer Japan, running errands for the Juppongatana. It can be assumed due to Ashitarō's possession of Mugenjin combined with is ability to perform its signature fire technique, Ashitarō may have either received training from Shishio or at least have seen the man fight.
- Akabeko Staff - One of the servers at the Akabeko comments that she found Ashitarō collapsed at their back door at one point. She appears to continue taking pity on the boy even after he moves into the dōjō, offering to allow him to work as a greeter and order taker at the establishment in exchange for a meal. (The status of this good will is unknown after Ashitarō started a fight with the police on the Akabeko's roof)
Ashitarō is shown to but a competent swordsman, being able to fight off several members of the police force without needing to resort to drawing his blade. When engaging with Kenshin, Ashitarō becomes enraged and releases Mugenjin from is sheath, igniting it and causing the boken that Kenshin is using in place of Sakabatō to catch fire and become useless.
He is noted several times to lack the ability to read and write, and when pressed claims that he doesn't need those skill. It is noted that his comprehension of written language is roughly the same as Kenji (who is about 4-5 years old)
Not much is known about Ashitarō prior to him arriving in Tokyo. Due to comments by various characters it can pieced together that:
- He served in the forces that Makoto Shishio intended to conquer Japan with as an errand boy for the Juppongatana.
- At some point after Shishio's defeat, Ashitarō came into posession of Mugenjin. The sword is missing a Tsuba and its Ito has become ragged (mimicking Ashitarō's own appearance). Due to the fact that Mugenjin burned while in Shishio's possession at the end of his fight with Kenshin, then was buried in the collapse of the mountain stronghold; it is likely that the blade has been reset into an entirely new Tsuka.
- Ashitarō was found collapsed on the back step of the Akabeko at some point.
- At some point in the past Ashitarō was arrested for walking out on the bill for a meal.
- Ashitarō is familiar with Kubota Asahi because she once gave him food.
- Ashitarō has seemingly never received any education besides swordsmanship, being baffled by seemingly both written words and numbers.
- Ashitarō lives full time at Kamiya dōjō, and is accompanying Kenshin and Kaoru to Hokkaidō for reasons that have not been explained to him (or the reader) yet.