when you move to Johto. all your kanto pokemon in your team get put in your PC Box and become locked, same with all the kanto pokemon you caught. you start of with only your items in your bag, you then get a starter and start from begining, i do recommend when you get to the 3rd gym to buy high level pokemon. or if you have friends that play and have finished johto, you can borrow a pokemon (you can only have johto pokemon even traded pokemon have to be johto) until you get the 8th badge then all kanto pokemon become unlocked :)