Big Brother is Little Sister and Little Sister is Big Brother

Youta and Hikaru, a twin pair of siblings, have grown up together and been close all their life. Since their parents are gone from dusk til dawn running a bar, Youta has stepped into the role of housewife of the family, cooking, cleaning, and generally getting things done. His twin sister Hikaru has always had trouble showing emotion, thereby leading to people misunderstanding her and showing fear of her. One morning after certain things come to light about their family, Youta and Hikaru are involved in a car accident. Upon awakening, they find they've switched bodies!