The anime is set in the birthplace of the popular card game Rush Duel, Mutsuba-cho. Twins Yūhi and Yuamu run UTS (Uchūjin Trouble Sōdansho or Alien Trouble Consulting), a group that (supposedly) gets rid of troublesome aliens from distant sectors of the galaxy via Rush Duel battles. However, one day, they find an actual spaceship, and inside they find Yudias, an alien from the Belgar Cluster. Yudias has come to Earth to search for Rush Duel to hopefully lead him and his friends (who have been chased out of their star system) into a new future. However, Yudias himself knows nothing about Rush Duel. Yūhi then challenges Yudias to a duel.