There is not much to this chapter but a lot of talking, back story, exploring theme park, and fun game. Start by saving your game and just follow the yellow marks until you board a submarine (there are 2 submarines so board the one with yellow mark). Here, you will notice 7 paths that look like octopus's arms, go to the first path in clockwise direction:

• ITEM (T-01): Phoenix Down (x1)

That is all in this area, but you can hang out and take some photo/screenshot if you want. When you finish, go through the main path until the game ask you to play a mini-game, finding Chocobo Chick.

1. First spot to find it is in a flock of baby sheeps. 
2. Second spot is on the merchant cart.
3. Third spot is on top of the fountain.
4. Last spot is in a flock of Chocobos near the merchant cart.

Easy game right? Now collect your reward:

• ITEM (T-02): Star Pendant (x1)

That is all in this area. Continue your way to the yellow mark. Before you get into battles, let's spend our Crystarium Points: Synergist for Sazh and Saboteur for Vanille. Then equip Tungsten Bangle and Iron Bangle on both of them.

• ENEMY (E-01): Corps Gunner (x6) (FIRST ENCOUNTER)
• ENEMY (E-02): Orion (x1), Corps Gunner (x3)
• ENEMY (E-03): Zwerg Metrodroid (x2) (FIRST ENCOUNTER)
• ENEMY (E-04): Zwerg Metrodroid (x1)
• WEAPON (T-03): Spica Defenders (x1)
• ENEMY (E-05): Zwerg Metrodroid (x2), Corps Gunner (x3) (LAST ENCOUNTER)
• ENEMY (E-06): Zwerg Metrodroid (x3), Orion (x1)
• ENEMY (E-07): Orion (x1) (LAST ENCOUNTER)
• ACCESSORY (T-04): Guardian Amulet (x1)

Go straight pass the Save Point toward the dead end for another item:

• ENEMY (E-08): Zwerg Metrodroid (x6) (LAST ENCOUNTER)
• WEAPON (T-04): Healer's Staff (x1)

Backtrack to the Save Point and prepare for a boss fight.

Paradigm (Sazh/Vanille):

• COM/RAV (default)
• COM/MED
• SYN/SAB
• RAV/RAV
   
• BOSS (B-01): Midlight Reaper (x1)
  Strategy: 
  • Cast 1 Libra.
  • Start with SYN/SAB. Sazh casts Haste, Bravery, Faith on both Vanille and Sazh, while Vanille should have casted Imperil on the boss. 
  • Once the setup is ready, go full offensive by switching to COM/RAV and RAV/RAV (1 turn each) until staggered. 
  • During the offensive, you probably switch to COM/MED a few times to heal.

It is not ended yet because there is another boss waiting for you. It sucks if you lose though because you will have to fight Midlight Reaper boss again.

Paradigm (Sazh/Vanille):

• COM/RAV (default)
• COM/MED
• SYN/SAB
• RAV/RAV
   
• EIDOLON (B-02): Brynhildr (x1)
  Strategy: 
  • Cast 1 Libra. 
  • Start with SYN/SAB and cast Haste, Vigilance, Bravery, and Faith on both. Vanille should have sticked Deprotect, Deshell, and Imperil on Brynhildr.
  • Now, it's time to rack up Gestalt gauge. The gauge fill faster when you can chain your combos and quickly raise the stagger meter. To do so, switch between COM/MED and RAV/RAV (COM/MED when low HP and RAV/RAV to quickly raise stagger meter).