The appearance of Mephistomon causes Bio-Merging of Digimon to happen all around the world and it's up to the Tamers to stop him.

Mephistomon is a Digimon born from the data of Apocalymon and is out to conquer both worlds after evading Omnimon, the protector of both worlds. Meanwhile, Takato is visiting his cousin Kai in Okinawa and Henry is off scuba diving the same day as computer creatures called V-Pets are created. But when Digimon start Bio-Merging in the Real World, the Tamers must stop them and protect Minami Uehara, the daughter of V-Pet inventor Takehito Uehara. Can they stop the evil plans of Mephistomon? And what does a Digimon named Seasarmon have a purpose in the battle against Mephistomon?—Rtkat3