Where do you find johto pokemon in firered?

Answer 1

In the Sevii Islands, specifically Sevii Islands 4-7. You can only go there after you defeat the Elite Four. I suggest packing a pokemon with False Swipe(Marowak caught on Victory Road know it), because most of the Johto pokemon are very low-levelled. However, you cannot get all of them. No starters, Houndour, and a few others.

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