Akai Taiyo has been lonely since her mother, her only blood relative, passed away a year ago. However, she has a cheerful personality that doesn't let that affect her, and her childhood friend Kotaro secretly has feelings for her. Then one day, Taiyo's father, Takashi, suddenly appears and persuades her to move in with his new family. However, her stepmother Yumiko and her half-daughter Momoka treat her like a housekeeper, and Momoka's fiance gives her lewd looks. To top it all off, Kotaro suddenly becomes close to Momoka...