Ken Takayanagi, known as Ken-chan, grew up as Azusa Noyama's childhood friend. His family runs a ramen stall close to her apartment, ensuring frequent contact since Azusa orders there regularly. Ken-chan harbored unrequited feelings for Azusa, creating tension when her close friend Kaoru Nishino developed feelings for him. He rejected Kaoru's advances due to his affection for Azusa, yet Kaoru maintained her friendship with both. Gradually, Ken-chan opened up to Kaoru and their relationship deepened as they grew closer.

He formed a significant friendship with Yūnosuke Ogasawara, a transfer student in their fifth-grade class who became Azusa's primary love interest. Alongside Makoto Sakaguchi, Ken-chan stood as one of Yūnosuke's closest friends. He often teased Azusa using her childhood nickname "Azuki-chan," but also showed protectiveness, especially during moments of her romantic insecurity or jealousy concerning Yūnosuke.

His family life involves his father managing the ramen stall, while his mother is rarely mentioned or seen. Ken-chan's development saw him navigate shifting feelings, moving from solely pursuing Azusa to acknowledging and reciprocating Kaoru's affection. He participated in the "Club of Unreturned Love" formed by Azusa, Kaoru, and Tomomi Takahashi, reflecting his early experience with one-sided romance.