The Koi carp is the scatter symbol and you need 3 or more of these symbols to trigger the free spins. Surprisingly, this symbol appears very often on the reels so you can trigger the bonus round multiple times. I had a very long session playing this slot and I myself have triggered the free spins many many times. The thing with the free spins is that even though you can easily retrigger them you still do not win a lot from them. The most that I have got was something like 50 x bet and that was it. But adding this amount on your balance on a regular basis is not something I would complain about.
During the base game the payouts are not that big. The Emperor icon is the highest paying symbol but it does not come very often. The most that you can win from this symbol is 5000 coins. The wild in this game is the little Garden pictogram but it only appears on the three middle reels. That makes it a bit powerless during the base game. You would only like to see this symbol during the free spins when it triples the wins.