Shinichi is a man in his mid-40s, a salaryman with a wife and children, yet he harbors intense sexual feelings toward his mother, Emi. His inner turmoil begins after reading a certain post online. As he reads those words, the emotions stirring within him grow stronger each day until they become impossible to suppress. One day, he honestly confesses his feelings to Emi, and she replies simply, "Only once, and only outside the house." That response becomes a turning point for him, setting in motion a new development in their relationship.