Just to give some advice beside of what’s already been said in the other guides.
For ppl who is struggling with this, i would like to add that you could enable the auto combo function which make this even easier.
Also i found the Helter Skelter devils breaker to be very effective while smashing the crystal, if you like me didn’t have the preorder bonus. It does Huge damage on the crystal, and you should have enough time to get away without getting any damage
Even with the auto combo enable, i was also able to get S rank every time, on all the difficulties i’ve tried so far, with this method
Hope it helps