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S04:E01 - All Aboard
Takuya, Koji, Zoe, Tommy and J.P. are contacted through their cell phones (that later on transform to their Digivices) to go to the Digiworld. They take a train at an underground terminal and descend to the Digiworld where they are confronted by Cerberusmon. Takuya's Digivice is activated and the Digispirit of his Digimon is called, transforming him into Agunimon who battles Cerberusmon.