"The Digital World, unlike our own world, is not ruled by the laws of physics, or at least, not the same physics that control matter in our universe. You see; the Digital World is named such because it is a world comprised entirely of data that has either fallen into place coincidentally, or been purposely programmed into its current position.
Due to this, the Digital World is unlike your two-dimensional surface plane. Instead, it is comprised of layers, which overlap each other and are connected in a far-from-linear fashion. However, you need not worry about this, the physics of the Digital World emulate those of the physical world, and thus, you may think of it as a simple plane of existence. We understand you feeble minds wouldn't manage not to.
What are you doing here? You may ask yourself.
You see, the Digital World is under dire peril; and we, Digital Monsters, or Digimons, the inhabitants of this world are absolutely, one hundred percent unable to do anything about it. Thus, we NEED you. You are not in a position to argue, we do not wish to know your feelings regarding the matter, but above all, we do not wish you to oppose us. You will do as is required of you in order to save us, or you will face the same fate we will. Not death… but the utter and complete erasure of your existence. You have NO choice in the matter.
You see… we, Digimon, are unlike humans in many aspects. We share your speech and your conceptual ideals of etiquette, but as living beings, we are too different. We have powers over data of the Digital World, call it nature if it makes you feel slightly less confused, but it is a concept you will soon understand. We are able to evolve into stronger versions of ourselves, and we are not necessarily mortal, but as of now, we are unable to defend ourselves against an inside threat. A threat you will dispose of.
As I stated, Digimon evolve into more powerful versions of ourselves with the passage of time, and the strongest of us are those who've reached the Mega level. However, these Digimon have somehow disappeared, and I'm next if I don't continue to use my powers in order to preserve myself. With only Ultimate Digimon left to defend us, we're vulnerable. That's why we need you. You will be led by a group of partner Digimon, you will help and protect those who need you, you will overthrow those who wish to end us, and only then, you will be free to go; so good luck, chosen children… and Godspeed."