Ten years ago, Nozomi divorced her husband and raised her son Naoya all on her own. Enduring the hardships of single motherhood, she worked tirelessly until Naoya finally reached the age of university graduation. Having fulfilled her duty as a mother, Nozomi felt both relief and a sudden emptiness, as if she had lost her life's purpose. Then one day, Naoya invited her on a hot spring trip. Looking forward to this graduation journey—her very first vacation together with him—Nozomi sincerely anticipated the time they would spend alone together.