Saku, the stepdaughter of his new spouse, arrives as a new member of the household. The father had been enjoying peaceful days with her, but this tranquility doesn't last long. Saku gradually begins revealing her true nature, repeatedly engaging in behavior that unsettles her father. She tempts him by touching her breasts, whispering, "You don't have to hold back in front of me." As a man experiencing life with a teenage girl for the first time, he struggles with how to respond. Then, on his birthday, Saku gives him a shocking gift that profoundly shakes his heart.