i, who left my parents' house and works as a company employee in tokyo, came home to my parents' house for the first time in a while using my time off. my parents and grandfather live in my parents' house. my grandmother passed away recently, and my mother is taking care of my grandfather, who is half-bedridden and depressed. my father is indifferent to his family and is just a drunkard. one night, i heard a strange voice coming from my grandfather's room. was it a dog in heat? it was a voice like that. i, who was curious, quietly opened the shoji screen. then... inside the room, there was my mother happily stroking my grandfather's dick while having her breasts sucked by my grandfather...