common-law husband and beloved son

Akiko (Yukari) lives with her common-law husband Shozo and son Kenji. Akiko wants to get married as soon as possible, but Shozo refuses to become a father, and Kenji does not approve of Shozo doing whatever he wants to his mother, so their relationship is strained. One day, Akiko was washing her back in the bath to cheer up her son, who was not feeling well, but she was so worried about him that she made a mistake. And, although it was supposed to only happen once, the presence of the father, who is not related by blood, deepens the relationship between mother and child even more...