Definitely a strange, imperfect game but I ended up loving it. Where do I even start trying to describe it?
Well, it looks overwhelming at first but after the initial information overload the systems actually work well together and make for pretty fun gameplay once you get into the swing of it. There is a lot of menuing in between gameplay, and while I didn't mind it much because I needed the time to strategize anyways, it can definitely become a slog.
I think the game's biggest issue the key item/recruitment system. I didn't try and obtain every character in the first place, but going in blind it can be very hard to tell if you missed something in a scene that you are then permanently locked out of (for the rest of the run). While breaking obstacles to obtain the items adds an extra layer of strategy to what units you use, it is often a very tedious high-risk medium-reward endeavor. Also, the key item you need to get the good ending is hidden in one of the levels (behind an invisible block, among other things), and to my knowledge there's nothing in the game that even remotely indicates how to obtain it.
The story isn't much to write home about, but I like the way it is told "backwards", learning how many of the characters die after you encounter their spirits makes it feel like regaining a memory, much like the game's protagonist does over the course of the campaign. Also, every character (including NPCs) has their own little part in the larger story, and most have a pretty extensive web of relationships with one another. I didn't even realize you can get extra dialogue from them on the pause screen until I was 3/4ths of the way through, which kinda makes me want to play it again just to read more of it.
This game definitely seems like it wants you to play through it multiple times, especially with the near unfathomable depth of some of the mechanics (e.g. I barely used the Rush Count system in my playthrough) and the large roster of units each with their own strengths, specialties, and growth rates. Learning where every key item is in the scenes, how the knights are related to one another, the behavior of every enemy, etc, seems like a long but at least somewhat rewarding journey. Unfortunately it is one so long and arduous I'm not sure if even I would take it.
I think this game will always hold some special place in my heart just for being such an eccentricity, even for the experimental DS era. I'd love to see this type (genre?) of extremely wacky clusterfuck gameplay revisited, but I don't know if or how it would work.

What if we put more systems on your systems heavy tactics game, and then what if the interface to simply move and command units was a touch input bullet hell? Completely nonsensical as is the trademark of Dept. Heaven project, but damn did they finally get excess right. Delirious and intensely hard, at least watch some high level game play because commercial games will likely never circle back around to whatever the fuck is going on here. Also, sorry to my undergrad roommate if you're reading this, but you're never getting your copy back.