When they were both seven, Tango and Ako were betrothed. Unfortunately, Tango met his demise in a car crash, leaving his parents as the only ones alive. Everyone in the opposing automobile perished, except for Rikurou. In due course, Tango's parents welcomed Rikurou into their family, replacing Tango as Ako's intended. Nevertheless, Ako is agitated by Rikurou's lack of passion for the life originally intended for her late betrothed, Tango.