Chika, the youngest of three sisters, assists her family in operating the historic Tochiman Ryokan Inn located in Numazu's Uchira district. Her bold and competitive nature fuels a strong determination to protect her community. This drive finds expression through her secret identity as "Katy," a member of the vigilante group Million Dollar. Utilizing wind-based weaponry like air guns, Chika combats threats alongside her sister Shima, codenamed "Marcy," under the mission coordination of their mother, known as "Big Mom."

Chika and Million Dollar confront disturbances caused by miasma, a mysterious force agitating wildlife. Their non-lethal methods involve purifying afflicted animals using specialized equipment: air guns to disperse the miasma and a magical ocarina to restore calm. During group operations, they adopt coordinated action stances.

Chika maintains a close working relationship with her family in both inn management and vigilante activities. Her protective instincts extend to supporting others in Numazu, such as assisting Yohane with personal challenges. The family pet dog, Shiitake, serves as the inn's mascot and frequently accompanies Chika.