Netoshisu.

Haruno Kasumi and Haruno Ayato are related, however kasumi is a girl older than him, one day Ayato declares to him and promises that when he enters the same school as kasumi they will be more united, so they agree to make that happen, shortly after Ayato visits a porn website that was recommended to him, Ayato begins to become addicted to the content of some videos where a girl seems to look just like kasumi, however the situation will take an unexpected turn when discovering the truth behind everything….