After sacrificing family time for 40 years, Akira finally retired. To console him and his wife Hideko, who had always supported him, their daughter Fuyumi's husband Taro planned a 'hot spring trip.' Akira's heart pounded with excitement at the family trip he never got to take during his active years, feeling grateful towards Taro as they arrived at a certain hot spring town. Upon reaching the inn, Hideko soaked in the hot spring with Fuyumi. However, a man eyed Hideko's body suspiciously... Who was that man...!?
