After his father's remarriage, Yūta Asamura finds himself getting a new step-sister Saki Ayase, who happens to be the number one beauty of her grade, and lives together with her. Having learned the important values about man-woman relationships, seen through their parents, and in order to not cause discord in the family, Yūta and Saki promise to keep a reasonable distance from each other, not to be too close or too opposing. Saki, who is longing for affection from her family and worked in solitude for their sake, does not know how to depend on others, while Yūta is bewildered at how to properly connect to Saki as her older brother. Feeling somewhat similar, the two of them gradually feel comfortable living together. Will they be normal step-sibling or they fall in a emotion called "Love"?