Celsius
This chapter begins with the Gullwings rescuing Yuna from the Farplane vision. After the cutscenes on the bridge, follow Paine up to the deck of the Celsius. Rikku will stop you along the way for another quick conversation while Yuna is passing through the hallway towards the elevator.
After the discussion with Paine on the deck, make sure you…
- Grab the treasure chests in the engine room (six
Remedies, eight Hi-Potions, seven Phoenix Downs, and three Turbo Ethers). - Take a rest in the cabin.
As a reminder, have Yuna rest in the cabin at least once in each chapter. Resting now awards nothing on its own, but the Chapter 5 scene it unlocks is worth 0.4%, and it only plays if you rested in every chapter.
Back on the bridge, Buddy, Paine, and Rikku will talk again about what to do next, and you’ll get another 
Al Bhed Primer. Shinra will suggest checking the CommSpheres…
It’s time to get started on the first of three separate CommSphere “waves.” Before you begin this lengthy, lengthy task, it’s worth saving your game at the 
Save Sphere aboard the Celsius just in case you run into problems viewing any of the CommSphere videos (accidentally missing one, accidentally skipping, etc.).
Checking the “Celsius Complete” box adds the Story Completion Percent for the automatic scenes in Celsius.