アリエッティは歌姫の頂点「巫女姫」を目指すが、落選してしまう。Arrietty aims to become a "priestess princess", the pinnacle of divas, but is unsuccessfully selected. She is then offered a marriage to the beautiful frontier count Joshua, but it suddenly breaks off. Arrietty, who has had a rough time of it, is ordered to be sent to the frontier as a priestess. Even though the marriage proposal was rejected...! The slow-life otherworldly opera begins in the frontier!