A story of a deepening bond between mother and son, gradually evolving into romantic feelings. On their first trip alone together, they head to a quiet hot spring inn. Holding hands and chatting happily as they enter, their appearance evokes the image of a pure parent-child relationship. However, suspicious men emerge from the shadows, already doubting the nature of their relationship. When the son enters the room, mother Iroha tries to embrace him, but he teases her, instead inviting her first to a private outdoor bath. In the bath, as the son expresses his desire, Iroha gently embraces him, and the two passionately make love. Unseen by them, the men are secretly recording everything, having been hired by the husband to spy on this trip due to his suspicions about their incestuous relationship. Oblivious, mother and son continue savoring their intimate time together.