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.
Kei loves Hikari and is willing to do anything for her. He always tries to please Hikari in everyway. At first, Hikari considered Kei as an arch rival/enemy, but it is seen in the later episodes that, Kei's got feelings for Hikari, which she fails to realize most times, making Kei go irritated and confused. Although, Kei puts up with Hikari, knowing that he could never be mad at her. An example is in episode 3, in which Kei ate Hikari's riceballs even though it tasted bad, which Tadashi reacted that hunger is the best seasoning. In episode 22, Hikari kisses Kei on the forehead which shocked him but said that he accepts her feelings for him. They've been together since childhood. Hikari proposed their engagement. He proposed to Hikari in the final chapter with fireworks, though Hikari stated that if she didn't accept, he wouldn't win. Hikari and Kei are seen as a future couple.
Akira is Kei's childhood friend, just like Hikari. They have a close but often provoking relationship. Typically, Akira takes Hikari away from him when he gets too close to her or he tries something weird on Hikari. In one of akira's flashback,akira states that kei had an aura around him that said "don't approach me".Because Akira gets sick and tired of having Kei always win, she sets out to finally make Kei lose like the time when she sets traps on the challenge, although Kei still came out on top!
Yahiro is another one of Kei's childhood friends. Kei, along with Yahiro and Akira 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.
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 calls him "Master Kei." He and Hikari are also in the "After-School Takishima Club", a club admiring Kei, although this is only featured in the manga.