Rina Kurumi is a cute and smart high school girl who is watched over by Rando Masashi pretending to be her twin sister Yuna. Rina is a 18 year old girl who is often shy around others. At the beginning of the manga she is a freshman at Seika High, attending school but not really conversing with others. When Rando bumps into her on the street, she believes him to be Yuna Kurumi, her long lost sister. Rina's sister used to be best friends with her but an arguement with her parents leads her to run away from home. Rina blames herself for her disappearance. Not wanting her to be sad, Rando decides to pretend to be her twin sister and live with her in their home.