After moving into a new apartment, siblings are forced to live together in the same room. Mai, the older sister, attempts to draw her younger brother's nude figure as part of her university art club activities, but during the process, her brother's cock naturally becomes erect. The unusual situation of sharing a room gradually awakens forbidden emotions between them, deepening their relationship over the course of seven days. Her cute smile, gentle demeanor, soft sleeping breaths, and youthful, attractive body shake her brother's resolve, slowly driving him toward an uncontrollable passion. The closeness of daily life sparks the beginning of a new, taboo emotion.