Yoji Sasaki is Miyo Sasaki's father and the ex-husband of Miki Saito. He is currently married to Kaoru Mizutani, residing together with Miyo in their household. He cares for his daughter Miyo but struggles to navigate family issues arising from his divorce and subsequent remarriage. His inability to effectively manage these complex dynamics fuels Miyo's emotional difficulties, including her feelings of abandonment by her biological mother and conflict with her stepmother. The name "Yoji" combines the meanings "ocean" (洋) and "reign" or "govern" (治), while "Sasaki" signifies "bamboo grass" (笹) and "tree" or "wood" (木).