After the mother passed away, the Toujo family became a single-parent household with a father and daughter. The father worked hard for his only daughter, and Natsu, who resembled her mother, grew up diligently watching her father's back. However, Natsu had secretly developed feelings for her father that went beyond parent-child love. She would masturbate daily to suppress these feelings, but one night, when her father brought up the topic of remarriage, Natsu's pent-up desires finally exploded.