"Digimon 01" centers on a group of seven children who are transported to a mysterious digital world during a summer camp. Each child is paired with a unique digital monster, or Digimon, that evolves and grows stronger as they face challenges together. The children—Tai, Matt, Sora, Izzy, Mimi, Joe, and T.K.—discover that they are the "Chosen Children," destined to protect both the Digital World and the real world from impending threats.

The narrative begins with the children encountering their Digimon partners: Agumon, Gabumon, Biyomon, Tentomon, Palmon, Gomamon, and Patamon. They learn that the Digital World is under siege by evil Digimon, led by the malevolent Devimon, who seeks to corrupt the world and extend his influence. The children and their Digimon must work together to defeat Devimon and restore balance. As they progress, they uncover the existence of the "Digivices," devices that allow their Digimon to evolve into more powerful forms, such as Champion, Ultimate, and Mega levels, to combat increasingly formidable foes.

After overcoming Devimon, the group faces a new adversary, Etemon, who seeks to control the Digital World through a dark network. The children eventually defeat Etemon, but their journey continues as they encounter even greater threats, including the Dark Masters—Piedmon, MetalSeadramon, Puppetmon, and Machinedramon—who have plunged the Digital World into chaos. The children and their Digimon must confront these powerful enemies, culminating in a final battle to save both worlds.

Throughout the series, the children grapple with personal challenges and growth, learning valuable lessons about courage, friendship, and responsibility. Key relationships, such as the rivalry and eventual camaraderie between Tai and Matt, and the nurturing bond between Sora and Biyomon, add depth to the narrative. The story also explores themes of teamwork, sacrifice, and the consequences of power, as the children and their Digimon face moral dilemmas and difficult choices.

The climax involves a confrontation with Apocalymon, a manifestation of darkness and despair, who seeks to destroy both the Digital and real worlds. The children and their Digimon unite to defeat Apocalymon, restoring peace and balance. The series concludes with the children returning to the real world, forever changed by their experiences and the bonds they formed with their Digimon partners.