In 2004, the Digimon product line introduced the Digimon Chronicle storyline, which was initially speculated to replace the V-Tamer 01 manga. However, it featured mostly prose text, accompanied by six-page manga, in booklets that were included with the "Pendulum X" digital pets. The storyline was divided into four "chapters," each connected to a specific version of the Pendulum X.
The story revolved around Yggdrasil, a scientist computer that controlled the Digital World. When an overflow of Digimon occurred, Yggdrasil was unable to manage the load, leading to the Digital Hazard. As a solution, Yggdrasil created the "New Digital World," with three layers representing the past, present, and future - Urd, Versandi, and Skuld, respectively. Yggdrasil also launched Project Ark and the X Program to eliminate unwanted Digimon. However, some Digimon adapted by obtaining the X-Antibody program, making them more powerful and immune to the X Program.
To maintain order in the Digital World, Yggdrasil deployed the Royal Knights - 13 Digimon with the task of maintaining peace. In the meantime, three humans - Kouta, Yuuji, and Shinji - stumbled upon the Digital World and met their partner Digimon, Dorumon and Ryuudamon. While Kouta and Yuuji opposed Yggdrasil and the Royal Knights, Shinji supported Yggdrasil.
