Astlibra Revision Postscript Final Boss on Impossible Difficulty

First three phases aren't much trouble. Phase two and phase three have a really big size, so magic that are balanced around spreading its damage over a large area do really well, since pretty much all of the damage connects. I go to the right at the beginning of phase two to explore (it's just a normal dead-end).
In phase four, I sometimes struggle triggering the support attacks (can see me stop attacking and inch over, spamming up). Kuro's support interferes with my healing, so I probably shouldn't be activating hers (also makes it harder to see). The falling rocks and lasers one-hit me, so I make sure to use magic to heal from it if I can. Could probably go faster if I used magic that doesn't miss as much.
In phase five, it turns out aiming for the hands takes about as much time as dealing with the main body. Next time, I'll definitely just ignore the hands and aim for the main body instead. The water sword's melee and stab-the-ground,-ice-comes-out moves trip me up the most, so I maintain some distance. The fire sword's projectiles take longer to act, so they're easier to heal off of comparatively. I have a hard time dodging the move where lasers come out from the sides followed up by petrification, so I save up mp and just magic-immunity my way through it.
Doesn't seem like I got True End, and I dunno whether that changes the fight or not.
[Edit: The fight does change.]
Retrying from phase four doesn't save the equipment configuration changes, so I have to modify it every time. (On a related note, I'm not sure why I even bothered. I don't even consider that alternate fire magic as good, and I even changed it back for phase five. )
When retrying from phase five, immediately after fast forwarding the cutscene, it's possible to open the menu and have the modifications persist across attempts. My guess is that there's a checkpoint soon after the cutscene, and retrying sends the player back to before the cutscene.
I show the Battle Record, equipment (had to re-equip, but I'm pretty sure it's right besides the order), Grow, Libra and Karon layout at the end. (Apparently, I forget to look at the status in my recording, whoops.) I'm not aware of any content beyond this point, so this'll probably be my last video on this game.
[Edit: Apparently there's still a bit of content left.]
Took a little under two hours to beat. Most of that time is spent on phase four and five.
Recorded on Dec 3, 2022.
Trimmed from my own playthrough on impossible difficulty, so don't expect a proper walkthrough/guide.
0:00 Phase 1
2:20 Phase 2
4:24 Phase 3
5:54 Phase 4
15:13 Phase 5
21:26 Battle Record and stats.