Yui, who lost her husband, lives with her son. Her son has withdrawn into himself, and Yui is taking care of him. However, that was just a pretense, and the two were aware of each other as the opposite sex even before her husband died... The mother of the second wife and the son of the first wife... Their feelings for each other grew stronger day by day, and they had already reached their limit. Yui wanted to put an end to this situation, so she invited her son on a trip to a hot spring... They were mother and son, but originally they were complete strangers... They wanted to stay connected... in both Kokoro and body... A storm of taboo pleasure hit them both.