Well Zanarkand has turned into a tourist trap. Yuna's not really happy bout that. We catch up with Isaaru who somehow doesn't really recognize Yuna. She still looks the same. Just not in a dress. So it turns out Cid of all people caused the tourist trap.
Anyway on with the story. We're here for a sphere anyway right? Traveling down we end up finding the Kinderguardians. Another Sphere Hunter Group made up of kids. Or really Pacce and 2 unimportant characters. They mention part of a clue. "key"
Continuing on the way. We find Leblanc goon asking the the clue. It's "mon" .....keymon? Monkey?!
Yeah not that hard.
Further on we find Cid. It's at this point you make a decision. I believe this affects Chapter 5. You can either yell at Cid about how he's stupid to turn Zanarkand into a tourist attraction or you can keep quiet. I'm not sure what happens if you keep quiet I never chose it. Moving on.
Remember our clue? Monkey yeah that's the password. Isaaru wants to play games. Just call him out on it. Done...well not really still got a sphere to find.
Not too tough if you leveled sufficiently. Just watch for curse. At low HP he'll start doing its original moves. You might know what I'm talking about if you played FFX. Yeah you don't wanna experience those attacks.
So we got a sphere. Now to move on to the end of the chapter.
(I believe you can port back to the ship and get Guardian Beast as a monster now or its at the start of chapter 2.)