Takato, Henry, and Terriermon have been caught underwater. They tried swimming out, even digging out, but nothing worked. When they came across a small group of rookie level Otamamon, they started to follow them but an Ultimate Level Divermon attacked, but lost. After the fight, he explained that he thought they where hurting the Otamamon. They asked for a way out, he led them to a giant tube. Digimon have gone in, but none have come out. They tried the tube, they found out they could breath underwater. They found themselves at a library. In there, they saw Makumon. They went to a back room to find Shibumi. He explains that the upper plain above the rest of the digital world is where the ancient guardians live. But, the Saubren also lurks there. He explains that their digivices are actually called "Arks" and they are used for storing data. They notice a giant ark floating above them. They get inside and not knowing where they're headed to, Takato, Henry, and Terriermon take off.