A single-family home nestled in a quiet residential neighborhood surrounded by greenery. The daily life of the four-member household was supposed to flow peacefully. However, one day, the father and youngest son left for a week-long trip, leaving the house empty. Left behind were the cheerful mother Rihō and the eldest son, who couldn't help but steal glances at her graceful figure while secretly harboring forbidden desires. His gaze, however, was fixed on the family's beautiful new stepmother. Beneath the calm surface of their ordinary lives, a whirlpool of hidden emotions began to stir.