Being largely an experimental piece, you performed well!
The choir ahhs add much texture to this song. The attack on the actual sound patch, however, does not suite how you introduced them in the beginning of this piece well. The fade-in gave it an inappropriately rigid feel, whereas how you introduced the chimes were well-place, subtle, and a harbinger of the rest of the song's harmonious attitude. This is but a slight blemish and nothing over which someone should fret, especially since the introduction performed its intended function --- to demonstrate a particular sound under a given mood --- and transitioned to other parts effectively enough.
I like your choice of drums. They have simple yet interesting rhythm that ties the whole piece together, and based on your description, it is safe to assume that its use in this composition was experimental. You did a great job, provided that is the case, as the piece demonstrates several instances of creative transition. It is pleasing to know that you are learning (I am far from being a musical cognoscente, but at least I can say that). Because of that, your drum set could pop out a bit more, so that it is not drowned out by competing sound, which tended to happen when multiple instruments started to play, notably the chimes and the choir ahhs.
Speaking of which, your choice of chromatic instruments for this Touhou track were noteworthy. The chimes (music box?), I felt, captured the elegance of the original track; the choirs captured the tension; and the piano gave life, mood, and tone. As for percussion, the drums provided the energy needed to sustain the song, as if they were the ‘heartbeat.’ Though, from what I hear, a bass would complement the drum set. It would give it that extra depth to the song, making it sound fuller.
The actual structure of the song is geometric to say the least, which I generally find attractive. You did it in such a way that the sounds do not become monotonous, incorporating enough transitions and additions to the piece to preclude such an outcome. After the sudden break rendered by a snare, should something be considered, the progressions began to feel restrictive (not to say monotonous). A bit a variety in the accompaniment would reinforce the composition already present strength behind your sounds. You outdid yourself, in that regard, with the pianos and the chimes. They sound harmoniously incredible, and the note with which you ended the song would be ample enough to replace the extended drums at the very end, when everything is done playing save the set.
Overall, the piece has a lot of effort placed into it and shows well from the product. I would love to a see an updated version of this, because as it stands now, there is some remarkable potential to be tapped. It is good (actually, you made me interested in listening to more Fires of Hokkai), but it can become great, but I suppose the same could be said to anybody.
I am glad to have listened to such an intriguing piece.