Maki goes on a hot spring trip with her son Kazuya. Kazuya, who is usually clingy and always wants to stay close to his mother, has been longing for this time together. This journey was meant to be a sex education trip, intended to help raise Kazuya into a mature man. Kazuya keeps suckling at his mother's breasts, unable to let go. Maki, captivated by her son's grown penis, begins to see him as a real man and guides him into sexual maturity. As their bond grows deeper, their relationship evolves into something new.