This animated comic is based on the visual novel "Haitoku no Oyakodon ~in'yoku ni Shizumu Mama to Imouto~" from the Studio Appetite, released in 2017. 

The protagonist of the story Koichiro-kun - simple very ordinary Japanese boy who lives with "nasty" younger sister Tokai Karina(86/57/86) and mother Ayako(89/59/90). His younger sister is very popular at the Academy among both boys and girls. Karina's good at everything in school and in the external data, it is good to all, except of course our hero Koichiro. For some reason, they have a terrible dislike for each other. Once Karina is so strong Koichiro displays of himself that he decides to punish her for all the bullying that she brought him. He decides to have sex with her against her will. Recording a video with a lecherous sex, Koichiro decides to blackmail his mother and also propositions her for sex...