Ten years ago, Sayuri divorced her husband and raised her son Tatsuya all on her own. Tatsuya has successfully graduated from college and now works at a securities company, seemingly living a stable life. However, he shows no intention of leaving home, and refuses to consider living independently despite her suggestions. He never goes out with friends or dates girls, and Sayuri begins to worry. Sensing something might be wrong in his life, she decides to invite him on a hot spring trip, hoping to offer warmth and comfort.