Rintarou's son. He's the scientist type and big pervert. He is also the older brother of Rintarou's two daughters making him the eldest. Kashitarou spends all his time alone on Juuren moutain in Juuren village until Gama and Zenmaru joined him for a year as he trained them.
He also seems quite perverted as he made lewd comments at Senka that later led to him being beaten to a pulp by her twice. In chapter 79, it was shown that he could do a double slash. His slash was so fast that Gama said it disappeared. He has a lot of knowledge when it comes to the body. Kashitarou was able to get past Gama using barely any movement and even got Gama in a vital spot.
Kashitarou is a very skilled swordsman but appears to have no stamina. When traveling with Gama, Zenmaru, and Shin to Jouka, they were perfectly fine while he was out of breath.