Shinobu, who lost her husband in an accident eight years ago, has raised her son Yuki on her own. The two are parent and child, but they had a physical relationship with a promise only once four years ago. After that, they lived a normal life as a normal mother and child, and eventually Yuki got a job and left home. As time passed by, Shinobu's mind was still haunted by the events of that day. One day, she invited Toshinobu to a hot spring trip as her last act of filial piety...
