Miki, who divorced 10 years ago, raised Naoya single-handedly. Naoya successfully graduated from university and got a job. However, Naoya didn't leave his parents' house even though it took more than an hour to commute, he didn't even go out on holidays, and he didn't bring his friends or lovers. Worried, Miki invites Naoya to go on a trip to the hot springs to let her go outside once in a while.
