Kaoru Takei is a first-year male student at Warabi Seinan High School. He has long light-brown hair, styled with bangs swept to the left, and light-brown eyes. While generally laid-back, he demonstrates fierce commitment regarding his feelings for Nozomi Onda. His long-standing friendship with Tetsuji Yamada began in childhood through football. During elementary school, they met Nozomi Onda and invited her to join their junior football league team. The trio later attended Fuji Daiichi Middle School together, continuing their football activities.

Within "Sayonara, Football," Kaoru plays as a forward for the Fuji Boys soccer team. He actively supports Nozomi Onda's bid for the newcomers' tournament. Upon learning she took her brother Junpei Onda's spot, he voices concern for her physical safety due to the competition's intensity. Later, during "Sayonara Cramer," he watches the practice match between Warabi Seinan and Kunogi Gakuen High School and later makes an offhand comment about the Warabi girls' performance, seemingly unaware of their emotional state post-match. He also attends the Saitama Preliminaries as an audience member alongside Yasuaki Tani, Tetsuji Yamada, and Junpei Onda.

His significant relationships include membership in the Warabi Boys Soccer Team with childhood friends Tetsuji Yamada and Yasuaki Tani. He shares a past teammate connection with Junpei Onda from the Fuji Boys Soccer Team. His defining relationship is with Nozomi Onda; they were childhood teammates on the Fuji Boys Soccer Team, and he harbors an unrequited romantic interest in her. Kouzou Samejima was his coach with the Fuji Boys. His name "Kaoru" translates to "fragrance" or "fragrant" (薫), and "Takei" combines "bamboo" (竹) and "well, mine shaft, pit" (井). He enjoys being in the spotlight.