On a sudden whim, Koyomi relocates to Tokyo, only to find that she has taken up residence right beside a boy she had taken a fancy to during her high school days. However, when she ventures to his house to pay him a visit, she gets a surprise, receiving instead a warm greeting from a girl whom she assumes is either his girlfriend or elder sibling. Imagine her astonishment when she discovers the girl is none other than the boy himself, Shirohai!