Kanade, a university student, visits his girlfriend Aimi's house for the first time. There, he is introduced to his younger sister Kaede, who is cute and free-spirited, with her braless breasts peeking out from the gaps in her clothes. Her body is bigger than his girlfriend's, and he is completely erect when she shows him her body without realizing it. Perhaps noticing his excitement, the devilish younger sister presses her G-cup breasts against him and seduces him. "They're bigger than your sister's, aren't they... will you like them?" Kanade, who has reached the limit of his patience, succumbs to his desires and fucks him every day... A scumbag boyfriend who is aroused by a sense of immorality.