-( Story related, cannot be missed )-
The main focus of completing this chapter, outside of reclaiming Sarasa's rampant fragment, is to clear the Sephirot that attempts to attack Hoshinomiya. Hopefully you've utilized the fragments you've obtained up to this point and invested the Growth Points (GP) to increase your levels. If not, this will be a bit harder.
I went with having these stats for my characters:
Hina: 2/5/5/1
Yuzu: 3/31/5/4
Lime: 5/3/3/2
I believe after the first level up (1 to 2), each should have a usable area-of-effect ability available to them. Make sure to utilize this at least once during the second phase of the fight, to try and eliminate the body parts from causing you strife. Have the prime focus be on the main body, so you deal more damage to that and the additional pieces get the lessened damage. It optimizes the damage dealt as a whole if you do this, as the Area of Effect skills do less on anything that isn't the prime target, and the prime target in this case is what you want to kill; the body parts will constantly regenerate when they get to the middle of the timeline.