Yōji Sasaki is Miyo Sasaki's biological father and Miki Saitou's ex-husband. He divorced Miki during Miyo's elementary school years, contributing significantly to Miyo's sense of abandonment and subsequent emotional struggles. Yōji later remarried Kaoru Mizutani. He currently lives with Kaoru and Miyo, with Kaoru assisting in household duties. Employed at the city hall (specific role unspecified), Yōji's remarriage introduced tension into the family. Miyo perceived Kaoru as attempting to replace her biological mother, feelings Yōji failed to adequately address. This lack of effective parenting during the family transition fostered Miyo's feelings of neglect and became a factor in her escapism through transformation into a cat. Physically, Yōji has brown hair and brown eyes. His surname "Sasaki" combines "bamboo grass" (笹, sasa) and "tree/wood" (木, ki), while his given name "Youji" incorporates "ocean" (洋, you) and "govern/reign" (治, ji). His established role centers on the family context and its impact on Miyo.