Keita is studying hard for a high school entrance test, but his two beautiful elder twin stepsisters are a constant distraction. Though they mean well, Ako and Riko are also extremely sexually assertive and interested in Keita. At first, he fends them off, but little by little, with each kiss, Keita becomes close to both twins until a forbidden love triangle develops. Will taboo-breaking love bloom between two of them... or will Keita at least get into high school?!