Smart, attractive, athletic, and talented like Yukino, Soichiro Arima becomes Yukino's competitor at school. Very handsome and popular, Arima excels at kendo and becomes a national champion. Although Yukino first hates Arima and tries to beat him, they eventually fall in love. After getting to know each other, Yukino learns that Arima, like her, is making an effort to "be perfect" for a reason.
While Yukino is motivated by vanity, she learns that Arima is trying to cover his real self, a self that he fears may be ugly. While Arima comes from a distinguished family of doctors, he was abandoned by his parents, who were the family's disgrace, and raised by his uncle and aunt. Fearing that he may turn "bad" like his parents, he is always trying to hide behind a mask and is constantly fighting his own demons. As with Yukino, he feels more in touch with his true self as he falls in love. But along with love, he is apprehensive of his other emerging emotions, such as becoming increasingly jealous of Yukino's friends, her activities, her life without him.