You'd all be making your own characters. As for how sex would fit into this, well, this is an underground tournament. Trainers from all over are abducted and kept against their will. The organization running this will profit from the people who pay to see these fights. And to help increase profit, the loser has to submit to the winner and put on a show. At least, that's the idea that I had. Like I said before, if other people here have other ideas, please share them.
Also, trainers wouldn't have to be abducted. Your trainer can enter the competition voluntarily if you would prefer.
Carlissa, as far as pregnancy, that'll be something for you to discuss with whoever you want to impregnate you. Unless you were already wanting to start off pregnant?
Nyarly, I'm a bit hesitant about "gijinka" pokemon, but if the other people wanting to do this roleplay would like to use them, then I think it would be okay. And yes, the trainers would be older.