HOORAY GUYS!! I FINALLY BEATED IT~!

It was surprisingly easy, and I used kusanagi in the place of katana... with the buffs, dark sword and stuff, she was delivering over 20k damage in a single hit of Paschal Moon Slash (but that was probably a crit) Well... gonna try the katana later and see which one is better.
And I made some equipment modifications:
Youmu = Makai Ring, Strength Ring IV, High Ribbon (I noticed some damage difference when Youmu was taking damage from the boss' fire/ice attacks and stuff with the Ribbon equiped, but that's just me. And I gave her Makai Ring because the stupid boss for some reason used Minus on her instead of Alice once. And naturally, Youmu was killed in one hit)
Alice = Cumula Amulet, World Olympics Flyer, Hakutaku's Ribboned Horn (Cumula Amulet because it was the best replacement of Makai Ring I had, and I had to keep WOF because without it, alice would get a Triangle in Slash due to the Amulet, and that'd really not be good due to Samidare Slash. The third one is for full protection against petrification)
at the least not with what he's using and his level
It's sheeeeee!! SHEEEEEEE!! Why does everyone keep calling me a "he" here...? ?-?
Those points aren't doing a thing in DEX anyway.
No no no no! Those 4 points in DEX are there for a purpose. My byakuren got 88 IND with Launch Earrings IV equipped, but for each 2 points in DEX, you get 1 point in IND in return... so, with those 4 points, I can achieve 90, which is going to give me a 135%+ buff enchancement for weapon bless, given that according to my calculations, you get a 15% PATK buff boost for every 10 points in IND. So... if I left it as 88, I'd only get a 120% buff enchancement.
You should really consider crafting the Autobarrier shield for Alice if you still have an orichalcon left over. In expansion, orichalcons are super easy to get, so don't worry about that.
Well, I used the only Orichalcon I had to craft Magus Suit for Sanae due to Mystic Resistance... but gonna get this Autobarrier along with Yata no Kagami and Yasakani no Magatama when I start playing expansion.
You want, 13 Manussya, 16 Asura, 7 Half Ghost, 20 Sword, 9 STR. You don't need ranks in Katana, I don't think you can use Law of Spirit Calming without a Katana.
I hope one of your party members is Reimu, because she and Alice alternate protecting your team members. Reimu can use Super Duplex barrier and prevent Magic damage, so for that turn all magic damage is negated. This is one of the ways to negate Void Gravitation. For your last party member, if you can, have someone who can use dark element attacks to turn the field dark. Satori is also a good choice here if you want another user that can deflect things. Her magic reflect is useful in this fight and I believe it can reflect Void Gravitation. She also has Starlight Barrier, which is kind of useful and she can heal.
Alright, I modified the ranks distribution accordingly. And yeah, there's no way to use the "self" spells without a katana.
I left Reimu and Satori on the 1st party. I think alice can protect the party better on the 3rd phase than reimu, since Little Legion has a lower cooldown than Super Duplex Barrier, and while it's cooldowning, I can simply use Nitori's Hyper Camouflage support skill for some protection.
...I think you ground a bit too much :V
It wasn't that hard to reach this level while you're grinding with stage 21 mooks with a Yukkuri Crown and Yukkuri Medal equipped. :V (Yes, somehow I was able to get them. Seems like lady luck likes me)
Just by fighting everything (except for the Two-Headed Dragon because dear god that thing is like a pile of trucks) on stage 21, I got half of my party to level 70 (on Weekend, obviously). I feel that grinding for levels is completely unnecessary in that version, especially since everyone left stage 20 at around level 55 too.
Oh god... don't get me started on that Dragon. I was never able to defeat it. Although, it's mostly because I wasn't using my party properly. On stage 21, I was using a party to kill most of the possible enemy formations from the stage in general, and not a team to specifically kill that dragon. (Nor that giant with multiple arms for that matter)
My team consisted of Hyper Library Formation with Youmu, Byakuren, Patchouli, Marisa and Reimu (To prevent the stupid mindflayers mind blast or that breath attack from Machine Dragon/Enemies with store power)
By the way, I like how the game used some recurring Final Fantasy enemies along with other stuff. We have: Malboro, Mindflayers, Chimera, Adamantoise, Abyss Worm, Hydra, Catoplebas, Cockatrice, 2-Headed Dragon (Complete with the ridiculously powerful physical attacks), the puddings with high physical resistance and weakness to magic... etc.
I'm surprised that with so many of them in the bestiary, there is no Tonberry, Coeurl, Ahriman and of course... the classic Behemoth (How could they forget him?) and many others could be included as well.
Anyway, this game was quite much THE GAME for me. It's been a while since I last played a fresh old-school RPG and felt so nostalgic. But there's still stuff to do on expansion, and I'm aiming towards it. However, first I'm gonna play the game from start again till Muenzuka because I only started recording my boss battles from Garden of Sun and above. (Didn't bother with it at first because I thought the game would be too hard for me to finish). And once I'm done with that, I'll have a complete video collection from the main game's bosses to post on youtube.