Hmm. "Shackles" is prog-rock, but all synthesized. Sound quality and instruments are similar to what we hear on the "The Mysterious Island of Souls" episodes from Lost Files and Alphabet Planet.
As for the composition itself, it's exactly what you'd expect of Kikuta prog-rock. It's more like Mysterious Island of Souls and Soukaigi than anything, but not as colorfully arranged, not as harmonically or melodically complex, and just simpler in general.
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