One day, Minato meets a girl named Musubi, who literally falls out of the sky on top of him. Minato soon learns that she is a "Sekirei", and she chooses him as her "Ashikabi", one of the mysterious set of humans that have the genetic trait and can make a contract by kissing the Sekirei; this binds the Sekirei to the Ashikabi and allows them to use their full power in elimination battles with other Sekirei. Made up of 108 cute girls, attractive buxom women and "bishōnen", the Sekirei fight in a competition known as the "Sekirei Plan" organized by Hiroto Minaka, the chairman and founder of the mysterious and powerful MBI Corporation.