Ami, who has been trusted by those around her and has completed many jobs, is now in charge of training Mizuki, who joined the company this spring as a new graduate. However, Mizuki is good at her job, but she is cheeky and does things at her own pace, which gives Ami a lot of headaches as her trainer. At that time, Mizuki, who is usually good at her job, was working overtime, which was unusual for her, so Ami reluctantly stayed behind with her as her trainer. Then, Ami missed the last train, and at Mizuki's suggestion, they stayed in the same hotel room until morning...