This movie takes place after the Adventure series ends. It begins when a new Digimon Egg is found on the internet, and manages to penetrate into almost every computer system in Japan. When the egg hatches, it's identified as a new kind of Digimon, a Virus-type. It sustains itself by eating data from various system, and starts wreaking havok in Japan. As it consumes more and more data, it continues to evolve. And Taichi and Koushiro decide it's time to stop it.

They're off, sending Agumon and Tentomon through the internet to fight off this new enemy. But, with the Virus controlling systems like the American military, all too soon, this digital menace may become all too real. Calling in the help of Yamato and Takeru, they hope that they can stop what's already begun, and maybe save this world a second time.

(Source: AniDB)

Despite the recent Akuma attack, the members of the Black Order are in high spirits as they set about moving to a new base. Immediately upon his arrival, however, Allen Walker is suddenly called by the Central Agency and has his arm forcefully sealed by the Order. He is then led to a surprising meeting with his master, General Cross Marian, who reveals staggering secrets surrounding the enigmatic 14th Noah. A phantom thief incident, the arrival of a mysterious group of Exorcists, the death of an important comrade, and an all-out battle against the Noah Family—just what does this mean for Allen, Yuu Kanda, and the rest of the Order? This is but the beginning of a series of strange, seemingly unconnected events that lead to something far greater. [Written by MAL Rewrite]

The Yamadas and Chi move to a new apartment house, where keeping a pet is allowed.

Ever since her crush rejected her by insulting her appearance, Sunako Nakahara has been a shut-in with a hatred for beauty, embracing all things morbid and occult-related. She is sent to live in her aunt's mansion which, to her dismay, she'll share with four exceedingly handsome boys her age. Furthermore, her flighty aunt has made a deal with these boys that in exchange for living there rent-free, they are to turn Sunako into a proper lady by the time she returns from a trip around the world. Thus begins Sunako's hectic life with abrasive Kyohei Takano, ladies' man Ranmaru Morii, calm Takenaga Oda, and friendly Yukinojo Toyama. As she interacts with them she finds them less obnoxious, and she may not be as much of an outcast as she thought. [Written by MAL Rewrite]