Smart, attractive, athletic, and talented like Yukino, Soichiro Arima becomes Yukino's rival at school. Very handsome and popular, Soichiro excels at kendo and becomes a national champion. He is at first smitten by Yukino, unaware that she secretly hated him and constantly tried to compete with him. After unwittingly discovering that Yukino is not the model student everyone thinks she is, Soichiro blackmails her into doing his school work so he can spend more time with her. After resolving the issue and becoming each other's first true friend, they eventually fall in love. Arima has alot of issues with his past. He is scared that his family will hate him and reject him like they once did. However, because of that, he decided he had to become a perfect person. But, with Yukino's help he realizes his parents accept him for who he is and that he should love all sides of himself and show his real personality proudly to everyone.
He ran away from his old family and his new family adopted him. He was abused by his parents in the past. His adoptive father is the eldest brother of his real father hence his uncle.