Ten years ago, Shihori divorced her husband and raised her eldest son, Taichi, on her own. Taichi successfully graduated from college and started working at a printing company. However, his commute was long, sometimes taking over an hour, so Shihori suggested he move out and live alone. But Taichi refused to leave home, never went out on his days off, and never brought any friends or girlfriends around. Worried about him, Shihori decided to invite him on a hot spring trip, hoping it would encourage him to get out and experience the world a little more.