Miyo Sasaki, nicknamed Muge ("infinitely mysterious"), is a 14-year-old with messy light brown hair, light brown eyes, and average height. She habitually attends school barefoot or sockless, her uniform perpetually disheveled with her polo shirt partially untucked. Abandoned by her biological mother, Miyo resents her father's remarriage to Kaoru Mizutani, perceiving her stepmother as a replacement and resisting Kaoru's attempts to bond, extending this alienation to Kaoru's elderly cat, Kinako. Seeking escape, Miyo obtains a magical Noh mask from a mysterious Mask Seller, enabling her to transform into a white cat with bright blue eyes and light brown accents on her nose and tail tip. In this feline form, named Taro by classmate Kento Hinode after his deceased dog, she visits Kento regularly. As Taro, she listens to his personal worries, including his family's impending closure of their pottery shop, expressing genuine affection while hiding her human identity for fear of rejection. Miyo exhibits contrasting personalities. At school, she projects a hyperactive, rambunctious persona, initiating forceful interactions like her signature "Hinode Sunrise Attack" (a surprise butt attack) on Kento. This outward energy masks deep sadness and a tendency to withdraw, viewing individuals causing negative feelings as "scarecrows." Her obsession with Kento manifests as persistent, often inappropriate advances that strain their relationship. A pivotal moment occurs when classmates intercept and publicly ridicule Miyo's heartfelt confession letter to Kento, prompting his embarrassed declaration that he hates her. Devastated, Miyo impulsively relinquishes her human face to the Mask Seller, committing fully to life as a cat. This severs her human connections, causing her family and friends to search while Kinako assumes her human identity using the discarded mask. Trapped as Taro, Miyo experiences cognitive regression, losing comprehension of human speech and regretting her choice, especially after overhearing Kento express remorse. Her journey to reclaim humanity leads her to follow the Mask Seller to a mystical cat island inhabited by former humans who made similar trades. Kinako, recognizing Miyo's genuine connections, aids Kento in reaching the island. Kento uses a cat mask to partially transform and confronts the Mask Seller alongside Miyo. During a struggle within a supernatural realm, Miyo and Kento openly confess mutual feelings, prompting Kinako to return Miyo's human face. This intervention, supported by other transformed cats rebelling, restores Miyo. Following these events, Miyo undergoes significant growth. She reconciles with her stepmother, Kaoru, showing increased familial warmth. Her relationship with Kento evolves into mutual romance, evidenced by his reciprocated affection and playful imitation of her "Hinode Sunrise Attack." She demonstrates greater consideration for others' feelings and a more integrated, authentic self, moving beyond previous escapism and emotional facades.