Aya Arisugawa, Kaname Arisugawa's older sister, helps operate the family bathhouse. She possesses long periwinkle or light blue hair and purple eyes, typically dressed comfortably or in her school uniform. Her personality blends laziness with flashes of academic skill; Kaname acknowledges her strong learning capacity, though she frequently misunderstands important matters. Confusion comes easily to her. Aya's primary passion is video games, often pressuring Kaname to play with her. She streams online as "Ayapi," gaining popularity for her expertise. She masters new games instantly, rivaling players like Tsukasa Yuzaki. Impulsive actions, like commissioning then abandoning a backyard pond after seeing it on TV, are also characteristic. Since middle school, Aya harbored an unrequited affection for Nasa Yuzaki, sparked when he effortlessly solved a difficult math problem. She never confessed. Learning of Nasa's marriage to Tsukasa caused significant distress, initially provoking screams and shock when her mother announced it publicly. Despite the heartbreak, she chose to support their union to honor her first love. Her first interaction with Tsukasa involved awkward apologies at the bathhouse, including an unwelcome back-wipe and comparing Tsukasa's skin to an "iPhone X." She mistakenly assumed Tsukasa was Nasa's sister. Later, at a takoyaki party, Aya challenged Tsukasa to a video game match to test her suitability as Nasa's wife. After Tsukasa matched her skills, their rivalry shifted to mutual respect, with Aya adopting the nickname "Tsukachan." Her family background includes parental strife: her father abandoned her mother for a younger woman. Aya's attempts to share her romantic disappointment were dismissed by her mother as insignificant compared to this past trauma. She possesses specialized skills like exceptional sauna endurance, honed since childhood to withstand extreme heat.