After the mother's death, the Tojo household became a single-parent family with just father and daughter. The father worked hard to support his only child, and Natsu, a beautiful girl resembling her late mother, appeared to be growing up sincerely and responsibly. However, over time, Natsu's feelings toward her father began to surpass those of a normal parent-child relationship. Trying to suppress these emotions, she resorted to daily masturbation for comfort. But one night, when her father announced his plans to remarry, Natsu could no longer hold back—her pent-up desires erupted uncontrollably.