After divorcing her husband, Kaoru raised Yuki all by herself. Working tirelessly to spare him any hardship, she managed to send him to college. Before she knew it, Yuki was nearing graduation and had already secured a job offer from the city office. With parenting worries finally easing, Kaoru began enjoying the quietest days she'd ever known—until one day, Yuki invited her on a hot spring trip, saying he wanted to thank her for all her sacrifices. She accepted his invitation, and the two set off together on what was meant to be a graduation trip. This journey would become the moment that deepened their bond in ways neither expected.