The overall vibe for bullet hell fits pretty well, especially for "Lord of Ice" and "Guardian of The Fire". "Hand of The Night" feels like it builds up a little too slowly, but I feel like the elements are all there to make it a solid bop. Vocaloid works really well here and brings some nice variety to the soundtrack!
"At the end/edge of the world" was a cool concept, but it feels like they fell a little short impact-wise. I would have developed a bit more of a theme in the first track, maybe with a subtle piano or synth playing high notes to keep the focus on the feeling of awe and weight of being at the end of the world. This would give you a bit more room to build on in the fourth track.
Overall, the soundtrack has a very consistent sound to it and is pretty cohesive. The bullet hell tracks all bop pretty hard. Solid work overall!