It might be scene 4, I'm not too sure, depends on how the thing as a whole has to be edited. Watch this space for any scene numbery related changes.
This is the main focal point for me of the whole animation, where aria actually throws her entire surroundings back into the past. Just two backgrounds, an animated mask, and a whole lot of glowey FX.
Honestly though I think it lacks a certain impact, maybe the pacing's off, ideally there'd be a decent amount of blur and camera shake as the wave approached the screen, since I imagined it like a bomb shockwave blasting outward in slow motion. Steady but implacable.