The relationship between mother and son has always carried a special warmth. One day, the family of three planned a hot spring trip, but the father was suddenly called back to work and had to leave. Left alone together, tension and unease fill the air. While the mother is bathing, the son, driven by uncontrollable passion, impulsively barges in. The mother speaks out in shock and anger, but her reaction only backfires. Their desire intensifies, leading their relationship into uncharted territory. The mother ends up mating with her son—and it doesn't stop there.