Despite having numerous activities at his disposal, Rintaro Magami, a talented student of the nearby high school, feels unenthused with his daily routine, as he has explored all possibilities. In an attempt to spice things up, he teams up with Luna, a girl with seemingly no worth, to compete for the title of the next successor to the legendary King Arthur. Unfortunately, a serious problem arises when Luna foolishly sells the revered Excalibur sword.