When Kiyoka was 18, she gave birth to Yuki and chose to raise him on her own. To prevent him from suffering, she dropped out of college and worked late into the night, rarely taking time off. Thanks to her relentless efforts, Yuki was able to enter university, but all the while he carried a deep sense of loneliness. When Yuki turned 20, Kiyoka used up all her accumulated paid leave, and the two embarked on a trip to a hot spring inn together. However, rather than enjoying the journey, Kiyoka remained preoccupied with worries about her job.