After secretly looking at my boyfriend's phone, I discovered he was having passionate sex with my mother. (KEED-085)

Kaori is deeply in love with her boyfriend, Atsushi, but lacking funds for dates, she often takes him to her home. Atsushi receives a warm welcome from Kaori's mother, Saki. They appear to be a happy couple, but in reality, Atsushi and Saki have been having a physical relationship without Kaori's knowledge. They continue this affair secretly until one day, Kaori secretly checks Atsushi's phone and discovers their affair...