Q: MMD or Blender?

A:
Blender!
The model is MMD, but Blender has a plugin to import MMD files
I had some help from my partner to fix some weird texture bugs with the file
But other than that, all animations from start to finish were hand made in Blender

Q: Flying Mech Suit?

A:
Not as of right now, as I don't have the DLC (Shame on me)
I had some ideas for the mech suit already, which would be the big mascot suit that Korone had posted pics about every now and then, to keep it with being a "big and bulky" design, but that might change when I see the actual mech suit in-game myself.