It's a very simple game idea. You live in the real world when suddenly Pokemon turn out to be real.
Sounds basic right? The twist is that Pokemon don't appear in the wild. PCs, or rather computers that act like PCs, start appearing all around the world. With the PCs people can access every single Pokemon they've ever caught in games, any Pokemon plush they've owned, every card they've ever gotten, or whatever, and make them real.
Every government in the world has declared these machines dangerous, illegal to use, and have cordoned them off (moving or destroying the machines is impossible). Leaving only the people who have hidden the machines, or gotten to them before the cordon, with access to Pokemon.
The character you play as doesn't have any Pokemon. You may never had access to a PC or you simply never been interested in Pokemon before. Whatever the reason, you need to get Pokemon. How you get the Pokemon is up to you, but you need to get some fast.
There's a war arising, and nefarious groups are being created. The world is in danger and it's up to you, and your allies, to save the world.