Takanashi Shuusuke has a hobby of collecting pornographic books, DVDs and pictures. Nao is Shuusuke's younger sister. Rather than a cool older brother, she prefers the lewd older brother who desperately attempts to get a glimpse of her panties. One day, Shuusuke's childhood friend Tsuchiura Iroha, whom he had not seen for 10 years, appears before the two and immediately throws herself at Shuusuke. Thus, Shuusuke finds himself in a love triangle with Nao and Iroha.