Mariko has decided to marry a man whose son is not attending school. Her husband's stepchild, Yusuke, does not accept Mariko, his father's new wife, as his mother, and keeps his distance even though they live together. Wanting to deepen their relationship, Mariko tells him that she wants to support him as a family member and a mother, and Yusuke gradually begins to open up to her. However, Yusuke's school refusal remains unchanged, and when Mariko hears about it, she learns that he has failed in his relationships with women. When Yusuke asks her to learn about the female body, Mariko gently guides him, saying, "I'll start by teaching you how to kiss like an adult."
