Mika lost her husband in an accident and has lived with her daughter ever since. After her daughter got married, she started living with her daughter and son-in-law. Life as a family of three was happy, but there was one problem. She could hear her daughter and son-in-law having sex at night and her body would get hot. She would release that heat by masturbating. One day, the three of them were having a drink together. When Mika fell asleep, her daughter and son-in-law started making out next to her. She woke up but pretended to be asleep. After they were done, her son-in-law called out to her. He said he saw Mika masturbating and asked her to have sex. She refused, but her body couldn't resist. Then, one day, he made advances on her and she embraced him...