From the introduction:
This is a world both like your original world, but also vastly different. Creatures composed of digital data, known colloquially as Digital Monsters, or digimon, live within a parallel world which exists alongside the Human World, as well as a couple other parallel worlds. The majority of people are wholly unaware of the Digital World, but a few children have been chosen by the denizens of the Digital World to save it, while a few intrepid scientists have discovered clues to the existence of said world.
You enter this world during the summer of 1999, when a group of children destined to save the Digital World are about to be brought to it for the first time. You have 1000 CP with which to spend in this world.