"In the year 1966 nearing early summer... right now, reverberating in my head, is the strange tune if bells chiming." -Kaoru Nishimi.Kaoru Nishimi (西見 薫 Nishimi Kaoru ) is a protagonist of the Kids on the Slope series. He is a brainy young man who moves during the summer of his first year in high school from Yokosuka to his uncle's house in Kyushu.
Kaoru is relatively short compared to Sentarou with short black hair and large black glasses. He stands at 168 cm (5'5") and weights 57 kg (126 lbs). It can be noted that when his hair is pulled back, he bears a resemblance to the jazz pianist, Bill Evans. After the time skip within both the anime and manga, he grows his hair up to his shoulders.
Kaoru is an extreme introvert and socially awkward teen with a habit of throwing up when under stress. this is due to him moving often as a kid making him incapable or not wanting to form bonds with others. This may have been reinforced by the somewhat unwelcoming nature of his extended family (whom he is staying with). Kaoru starts to open up after becoming friends with Ritsuko and Sentarō with the latter, becoming both his best-friend and jazz partner and the former becoming a love interest and friend.
Kaoru is a wonderful pianist, shown to be classically trained and is described as a prodigy. He quickly gets the hang of playing jazz music with the help of Sentaro. He is also very smart becoming a doctor after the time gap.
Sentarou is Kaoru's best friend. They first met when Kaoru ran up to the roof to throw up, Sentarou confuses Kaoru for an angel and fights some older students so that Kaoru can sit on the roof. Although at first, Kaoru did not like the loud and somewhat pushy nature of Sentarou they quickly become friends. as time passed, they both learn to understand the pain of each other as well as push each other to move on. Kaoru was the last person to comfort and see Sentarou before the time skip and afterwards, Kaoru moves to the same island and Sentarou vows to always be there for Ritsuko and Kaoru & their child.
Kaoru fell in love with Ritsuko from the first moment they met, her involvement resulted in the very strong friendship of Sentarou and Kaoru. Within the beginning, the love between the two was one-sided on the part of Kaoru since Ritsuko was in love with her childhood friend Sentarou. After learning about Kaoru's feelings and realizing Sentarou had never seen her in that way, she later falls in love with him. After the disappearance of Sentarou, she and Kaoru have a falling out, but are still shown to have feelings for each other, still staying connected as friends through letters throughout the time skip. At the end of the series, the two are shown to have gotten married and Ritsuko becomes pregnant.