“Since I’ve decided to protect you, don’t leave my side without permission.” Yoshino Nina was born into a family of professional bodyguards. Blessed with a natural talent for protection and exceptional combat skills, she is the strongest girl around. However, Nina has always longed more than anyone to be a “cute girl,” so she abandons the path of becoming a bodyguard and starts working as an office lady instead. At the same time, she fully enjoys her life as a devoted fan of Luka, a member of the hugely popular idol group Riot. One day, after hearing the news that Luka has gone missing, Nina gets into an accident and is reincarnated in another world as a noble lady named Nina. There, she comes face-to-face with Luka, her favorite idol, who claims to be her fiancé. But Luka seems to be targeted by someone who wants him dead, so Nina offers to become his personal bodyguard. Determined to protect in this world the beloved idol she could not protect in her previous life, Nina vows to keep Luka safe no matter what. However, being so close to him makes her heart race nonstop…!