Nope. It's the door to the women's restroom, perhaps the only one in Ys. Japanese games are really big on not letting you into the women's restroom if you're playing a male character.
if that were true, falcom would probably allow him to walk in there and enjoy himself
Another question I had was the black rotating prisms right before that room I mentioned. You can shoot fireballs at them for a cool effect but thats about it. Are there any meanings to those or are they just decoration?
Not a far-out guess. The Black Pearl was the source of Ys' prosperity and we know it was Emelas. It's not impossible that Feena and Reah brought more of the stuff when they founded the city-state (such as the Mask of Eyes, another Emelas artifact according to Perfect Data). We'll see if YsC gives us more on the origin of Ys or if they drop that angle and have the Goddesses come straight from the Atlas Continent.