I've worked on this on and off for way longer than I'd like to admit, but it's finally in a stage I'm comfortable taking comments.
5.0 surround version (untested): http://www.kozanryusui.net/sakkyoku_nikki/20191101_surround.ogg
5.0 surround version (untested): http://www.kozanryusui.net/sakkyoku_nikki/20191109_surround.ogg
The titular castle is the 5th stage of Touhou Double Dealing Character (or Touhou Kishinjou), an inverted castle floating in the sky. The original title 空中に沈む輝針城 ("Kuuchuu ni shizumu kishinjou") translates to "Castle of the shining needles, sinking into the sky". I've tried to emulate a journey through the castle:
0:00 - 0:40: Enclosing onto the castle through the cloudy sky, eventually reaching the front gates (which you can hear open if you listen closely)
0:41 - 2:26: Journying through the increasingly grand corridors and halls of the castle
2:27 - 3:08: Slowly tracking back while basking in the afterglow
3:09 - 3:23: Falling out the main gate into the evening sky (the gate closes behind you)
I've loved this theme ever since I first played the game. It was the first 5th stage theme for me to finally knock the one from Touhou Mountain of Faith off its first place pedestral, and it has become one of my favorites in the entire Touhou music corpus.
Initially my main motivation for creating the arrangement was to mark the climax off with the bells at 2:12 and the rest of the arrangement was just fluff to get there. Later on the actual climax shifted two more measures to the part at 2:17 because I just love deceptive cadences.
The rest of the arrangement should be a very straightfoward orchestration. I've taken some liberties with the instrumentation, chord progression and custom counter points, but it's essentially a single run-through of the original song. The seating of the orchestra is German instead of American (second violins opposite first violins, basses to the left etc.) which is mostly noticable during the beginning.
Considering how much I fought with almost every aspect of the song I'd be grateful for any comments on pretty much anything. The 5.0 version is a byproduct of my workflow which I cannot test due to a lack of a surround setup, so please don't expect it to be well-engineered.
I'm not sure if this arrangement would cut it for submission-level quality. Judging from the other orchestral arrangements on the site so far I'm tending towards no, but I could only find either Hollywood-style arrangements (i.e. with lots of supporting percussion and/or non-orchestral instruments) or rather mellow arrangements which tend to be not as thickly layered, so I'm not really sure if these comparisons are any good indicator.