Okino Kazuki is a normal student who is happy with his staid life. There are two important girls in his life: his sister, Rinka; and childhood friend Sakuragi Otome. 
 
His elder by one year, Otome is a beauty and the dream of every guy in school. Although Otome and Kazuki aren't a couple, they hang out with each other constantly and get along very well. In fact, Kazuki believes that as long as things proceed as they currently are, the two of them will eventually be together as a couple, and even marry. 
However, Kazuki's faith is shattered one day when he receives a damning DVD... 
 
(Source: Official Site)