Name: Himura Kenji
Nicknames: Little Lion, Oro-chan
Weapons Attacks: Kamiya Kasshin-Ryu, Hiten Mitsurugi-Ryu (when he's older)
Closest Friends: Sano, Yahiko, Yahiko's son, Shinya
First appearance: End of the Revenge Arc
Biography: Unfortunately we only get a brief introduction to Kenji in the manga, and since I'm a manga purist, I disregard his depiction in Seisouhen entirely. In the character notes, Watsuki mentions that Kenji is a genius and is able to learn the Hiten Mitsurugi just by hearing about it. Being a genius doesn't necessarily make one flawless. Watsuki goes on to note that Kenji grows into a young man that's "more twisted than Saitou and more egotistical than Shishio". In other words, Kenji is a handful!
Now since a lot is left to interpretation, I try and interpret Kenji as a character. First off, I don't believe that he grows up hating Kenshin, despite him being shown yanking on Kenshin's hair as a toddler. He was two and was going through a phase where he preferred Mom to Dad. I believe that Kenji probably had a loving, albeit stormy at times, relationship with Kenshin. I'm certain that he would grow up revering his father even if he never saw him wielding the sakabatou. He probably saw his daddy doing other great things and heard stories from Yahiko and Sano about his father's battle prowess. I also think Kenshin was a very loving father and taught his son many things, including his beliefs in an effort to keep Kenji from treading the path he trod as a youth.
I see conflict arising between them as Kenji becomes older and develops his own personality, which is in fact, nearly identical to Kenshin when he was a boy, stubborn, headstrong and at times disobedient. Kenji wants to learn Hiten Mitsurugi, which Kenshin had intended to let die out with him. I can imagine Kenji being very angry with his father for refusing to teach it to him and then his father's chagrin when Kenji was able to mimic it even more successfully than Yahiko was able to, just by hearing stories about it. I can see Kenji clashing with Kenshin over the philosophy of non-violence. Whereas Kenshin would try to defuse a situation by talking, I can see Kenji as the type who would leap into the fray and fight till the enemy either gave up or died. This would put him at odds with his father.
No doubt the tensions between father and son will increase as Kenji goes into puberty. They would still love each other, but like any teenager and parent, would have their conflicts, especially when their personalities are so similar. Kenji would want to do things one way and Kenshin would insist he do them another. Watsuki's notes also say that Kenji battles Yahiko's son, Myojin Shinya for possession of the sakabatou. So do we have Kenji using Hiten Mitsurugi fighting Shinya, who uses Kamiya Kasshin? Could a Kamiya Kasshin swordsman ever beat a Hiten Mitsurugi swordsman?
Beyond this, I don't know what would happen to the father/son relationship. I don't know if Kenji goes on to be some evil, homicidal maniac, or if he mellows out once he's through puberty and is once again close to his dad. However, if I know Kenshin, he would never give up on his son. Kenshin and the others will persist with kindness and patience to try to bring Kenji back home.