Ayato Haruno is living under the same roof with Kasumi Haruno, the older sister of a relative whom he has longed for since his parents suddenly moved out on their own. In order to attend the same school as her, Ayato tries his best to study hard, but he finds it hard to concentrate. Then, one day, he happened to open an adult website and found an erotic video of a person who looks exactly like the person he admires...