Dan Bashin is a young Card Battler who dreams of winning the championship tournament of the trading card game Battle Spirits. One day, he follows a strange girl he meets at the championship. Suddenly he is flung into the Otherworld Grand Rolo ruled by Ikaiou. It is a world where Card Battles with Battle Spirits are the ultimate form of combat.
A 12-year-old boy named Dan Bashin is taken to the alternate world of Grand Rolo by two mysterious siblings, Yuuki and Kajitsu Momose. There, he learns that he's one of the chosen core soldiers, bearing the light of the red core. Along with the other soldiers, he must save Grand Rolo from Otherworld King, who has been exploiting the worlds natives.