"Digimon: Diaboromon Strikes Back" is a direct-to-video sequel to the 2000 film "Digimon: The Movie," continuing the conflict between the DigiDestined and the rogue Digimon Diaboromon. The story begins with the DigiDestined—Tai, Matt, Sora, Izzy, Mimi, Joe, T.K., and Kari—living their everyday lives after their previous battles. However, their peace is disrupted when a mysterious computer virus begins spreading across the internet, causing widespread chaos. The virus is revealed to be a new form of Diaboromon, who has evolved into Armageddemon, a far more powerful and destructive entity.

Armageddemon's goal is to assimilate all digital data, threatening both the Digital World and the human world. The DigiDestined reunite with their Digimon partners—Agumon, Gabumon, Biyomon, Tentomon, Palmon, Gomamon, Patamon, and Gatomon—to confront this new threat. As Armageddemon grows stronger by consuming data, the DigiDestined struggle to find a way to stop it before it consumes everything. The situation escalates when Armageddemon begins to manifest in the real world, causing physical destruction and endangering lives.

The narrative explores themes of teamwork, sacrifice, and the consequences of unchecked technological advancement. The DigiDestined must rely on their bond with their Digimon and each other to stand against Armageddemon. Key moments include the Digimon achieving their Ultimate and Mega forms, such as WarGreymon and MetalGarurumon, to combat the overwhelming power of Armageddemon. The climax involves a high-stakes battle where the DigiDestined and their Digimon push their limits to protect both worlds.

The film also introduces new elements to the Digimon lore, such as the concept of Digimon evolving beyond their known forms and the interconnectedness of the Digital and human worlds. The resolution emphasizes the importance of balance and responsibility in the use of technology, as the DigiDestined manage to defeat Armageddemon and restore order. The story concludes with a sense of hope, as the characters reflect on their journey and the enduring bond between humans and Digimon.