Kari and Gatomon are finally saved and they join Tai’s group. Komondomon dives into a sea current to head toward their next destination. As they make their way underwater, they come across a mysterious city.
Tai's group dive into the Net Ocean on their way to FAGA, the location of Millenniumon's largest piece, in order to stop his resurrection, but they are knocked out of the marine current and take shelter on an underwater city led by MarineAngemon. After spending the night in the city, the children are about to resume their journey when the city is attacked by Scorpiomon and a group of Mantaraymon. While the other Digimon of the group fight along their human partners, Gatomon insists on fighting alone to protect Kari, until Kari convinces her that they must fight together and Kari gains her own Digivice, using it to power up Gatomon who leads the others to defeat the invaders. After the battle, the children bid farewell to the underwater city and continue their quest to stop Milleniummon's return.
In the meantime, all efforts to save the ISS from the collision with the satellites have failed, and the remaining crew evacuate in the Soyuz spacecraft, leaving the space station to its fate.