Kyōka Mizukami is a young woman who works at the front desk of the advertising agency TEN2 alongside her close friend Yoshie Yamazumi. She is one of the main protagonist Tokine Amino's best friends, and the three often spend time together both at work and in their personal lives. Kyōka comes from a family that owns and operates the Minakami Hot Springs, a hot spring facility that becomes the destination for a company trip during the series. On that trip, Tokine and the group meet Kyōka's younger sister Kyouko, as well as Kyouko's high school friends Hinata Takaragawa and Mamori Sonazawa, indicating that Kyōka maintains strong ties with her family and hometown.

In terms of personality, Kyōka is portrayed as a supportive, dependable, and friendly individual. She willingly helps Yoshie with moving to a new apartment and participates in social outings such as dinner and the company trip without hesitation. Her motivations are not deeply explored, but she consistently demonstrates loyalty to her friends and a willingness to assist them in everyday matters. She does not possess any special abilities in the real world, and while she occasionally gets pulled into the alternate dimension Quizzun alongside Tokine and others, she does not actively solve puzzles or exhibit the enhanced capabilities that Tokine and certain other characters develop. In those situations, she remains a passive participant, highlighting her role as an ordinary person caught up in extraordinary events.

Kyōka's primary function in the story is to serve as part of Tokine's support network, providing a sense of normalcy and companionship that contrasts with the bizarre and unpredictable occurrences of Quizzun. She does not undergo significant character development or acquire notable powers, and her presence reinforces the everyday relationships that anchor Tokine to her regular life. Through her interactions, Kyōka helps ground the narrative in relatable, real-world connections.