Ayato Haruno, our mc get to live alone under one roof with his busty older sister, Haruno, because their parents was appointed for sudden assignment. Our mc attends the same school as hers. During study session mc having trouble with concentrating because his sister tits are getting in the way of studying and it is too hard not to look at them. . One day mc decided to confess to his sister, seeing how cute his brother is, she acceptepted his feeling but only just to meant to tease him, after a few days mc found naughty video that shows a person he knew, but he opened the video anyway. turns out her sister is a prostitute.