Kiyoka gave birth to Yuuki when she was 18. Kiyoka raised Yuuki single-handedly. To spare him any pity, she quit university and worked late into the night without taking a day off. Thanks to this, Yuuki was able to advance to university, but he always felt lonely. When Yuuki turned 20, Kiyoka decided to use up her accumulated paid leave, and they set off for a hot spring inn together. However, Kiyoka's mind was only on work.
