Four years ago, Kiyoka gave herself to her son just once. After losing her husband eight years earlier, the two had lived alone together, their bond growing deeper with each passing day. When her son announced he would be moving far away for work, she granted his heartfelt wish and finally chose to unite their bodies. That night, at a hot spring inn, beyond the boundaries of ordinary life, reason vanished completely. Yielding to her instincts, Kiyoka surrendered to desires she could no longer suppress. Now, once again, she finds herself walking the same forbidden path. Memories of the past pierce her heart, yet overwhelming emotions pull her back irresistibly.