Rito Yuuki's existence is a continuous onslaught of uneasy and inappropriate situations with girls. Despite his enduring love for Haruna, his childhood flame, he can't help but scrutinize his emotions for Lala, the extraterrestrial princess who appeared out of nowhere and demanded his hand in marriage. However, Lala isn't the sole culprit for the mayhem in his life; her identical twins, Momo and Nana, also come to Earth with the aspirations of meeting their elder sister's betrothed and ultimately end up bunking with Rito. Amidst the bedlam, Yami, the lethal human weapon girl, sets her sights on Rito. As he maneuvers through the turbulence of uncertain love, consequences for his pervy ways, and a girl determined to assassinate him, Rito's existence becomes an evidently arduous one.