I wasn’t able to find any reliable source that describes how Prince Arnold conceals his identity as Silver—things like disguises, magical masking, or separate physical traits—beyond the fact that he plays up his image as an inept, lazy, "insipid" prince to everyone else. The details of the mechanics of the secret id…
If you want, I can dig into up-to-date manga/novel content summaries or translations to see if there are chapter-specific reveals.
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