Aya Arisugawa, Kaname Arisugawa's older sister, helps run her family's bathhouse, a spot Nasa Yuzaki visits. She possesses long periwinkle hair and purple eyes, usually dressed comfortably or in her school uniform. Outwardly a gentle, popular beauty, her lazy and ditzy nature surfaces through frequent misunderstandings and confusion. Yet Kaname recognizes a "genius side," citing her exceptional learning capacity, especially her rapid mastery of video games. Her primary hobby is gaming, often pressuring Kaname into playing. She gained significant online fame as the popular streamer "Ayapi," dedicating real effort to building her channel. Aya demonstrates remarkable skill, quickly matching experts like Tsukasa Yuzaki even on first attempts. Another notable trait is her high heat tolerance, earned through childhood sauna training, granting her the title "heat wave master." Aya secretly harbored a crush on Nasa since middle school, developing feelings after witnessing him effortlessly solve a difficult math problem that stumped their class. She never confessed. Her family faced hardship when her father left for another woman, context later framing her mother's dismissal of Aya's heartbreak as less significant. Her first encounter with Tsukasa happened in the bathhouse; Aya inadvertently made Tsukasa uncomfortable by offering to scrub her back and comparing her skin to an "iPhone X," mistakenly assuming Tsukasa was Nasa's little sister. She later discovered Nasa and Tsukasa were married upon hearing Tsukasa's shared surname and her mother's confirmation. This shocked Aya, leading to a public outburst when her mother also revealed Aya's feelings for Nasa. Despite her heartbreak, Aya consciously chose not to sulk, determined not to devalue her first love, and mustered the courage to congratulate the couple. Initially struggling to accept Tsukasa, believing herself more suited to Nasa, Aya's perspective shifted during a takoyaki party at Nasa's. Intending to test Tsukasa, her hostility diminished as Tsukasa prepared delicious food. She then challenged Tsukasa to video games, winning repeatedly in Street Fighter V before Tsukasa prevailed when they switched. Exhausted after a lengthy session ending in a draw, the competition fostered mutual respect, leading Aya to develop a genuine friendship with Tsukasa, whom she affectionately calls "Tsukachan." Aya occasionally acts on impulsive ideas inspired by television, like convincing others to build a backyard pond only to lose interest immediately after completion. Her relationship with Nasa's cousin, Ginga Onimaru, involves constant bickering. She uses a Rei Furuya avatar on LINE.