This series is based on light novel of the same name. The main heroine, Rhino, is a cheerful gal who gets along with everyone. She also known as a madonna of the school because of her beautiful figure. On other hand we have an otaku who didn’t have much friends but pretty good at studying as the main character. They used as a total stranger, but now they became a step-siblings because of their parents’s remarriage. Day by day passes, Shohei’s starting to grows a feelings towards Rhino. Thankfully that they did shared the same common interest towards otaku culture, the two become close to each other in just short of time. From a classmates to a step-siblings and finally to a sex friends.