Kyōko Shirakawa, the eldest of the three Shirakawa sisters, shoulders significant household responsibilities and wields a dominant personality that shapes family dynamics. She stands 168 cm tall, weighs 52 kg, and possesses measurements of 98-57-86, with brown hair and red eyes defining her appearance. Her profession as a nurse anchors her daily life, yet after work, she occasionally drinks to disorientation, leaving her vulnerable. During one such episode, her stepbrother Yuu Shirakawa exploits her incapacitated state to collect her bodily fluids, required to break a curse upon him. This act initiates her ongoing participation in Yuu's mission to gather "love juices" from her and her sisters, filling a cursed jar to nullify its effects.

As the eldest sister, Kyōko engages alongside siblings Ryouko and Anzu in a shared dynamic as Yuu's partners. She partakes in intimate encounters with Yuu, frequently jointly with her sisters, as part of the curse-breaking ritual. Her character merges authoritative familial conduct with compliance in the curse-related scenarios.