Kei is one of the main protagonists in the series. He is ranked 1st
in the entire school which is why he has the habit of calling Hikari
"Miss Rank 2". He is the son of the CEO of Takishima Corporation, making him next in line for the company. He is Hikari Hanazono's undefeated rival. Kei became Hikari's boyfriend and they engaged which makes Hikari his fiancé.
Kei has messily styled light brown hair that tends to hang in his face and calm brown eyes. As he is in the S.A program, he wears the standard S.A uniform: a white blazer with the S.A. logo near the pocket, pale blue shirt, black tie, and dark blue pants. During the warmer seasons, he, along with the other male S.A. members, wears a short sleeved white shirt with the S.A. logo on the sleeve and near the pocket, green striped tie, and green pants. Whenever he is challenged to a physical contest by Hikari he usually changes to a plain blue t-shirt and some white pants. Outside of his uniform, Kei tends to dress very modern and sporty. At formal events, he wears a navy blue suit with a gray waist vest and light purple tie. When challenged to a physical event, he tends to rip off his tie.
Yahiro is another one of Kei's childhood friends. Akira,Yahiro, and Kei were all childhood friends when they were young because of their parents' jobs, although Yahiro wasn't as close to Kei as he was with Akira. Yahiro was like a prince, always bossing Akira around and making tea for him everyday. Soon, Yahiro became a bully to protect Akira because other kids would just hang out with her because she's rich and they get presents when they go to her house, so Yahiro would threaten those kids to stay away from Akira or his father would take away their parent's jobs. Yahiro then develops a crush on Akira, but, Akira loves Tadashi, making Yahiro jealous.
Aoi admires Kei although he is 3 years younger than him. Kei and Aoi both have photographic memories and are "different" from others. At first, Aoi disliked his talent, but Kei told him they were "special" and since they are alike, Aoi looks up to him and call him "Master Kei." He and Hikari are also in the After-School Takishima Club.
Kei has a very bad relationship with his younger brother because Sui thinks he's a robot under human flesh. He feels inferior to Kei who is 'perfect'. But, thanks to Hikari, their relationship got better. sui then developes a 'brother complex'.
He is often dragged by his father along to work, usually foreign business meetings. It is revealed in the manga that he has a father complex and that he learned most of his skills from Satoru.
Midori is Kei and Sui's mother. Both of them inherited their looks from her, so they have a strong resemblance to her. She longs for the day when Kei will ask her to buy something for him. They aren't really that close since Midori is always working overseas.