For people looking this up, removing a Toto Aquia toilet seat can be a little tricky.
The toilet comes with long bolts and rubber "bushing nuts." These bushing nuts are inserted into the seat-mounting holes, the seat is placed over the bowl so the bolt holes line up, and then the seat is fastened down with the bolts. Now, the bushing nuts are rubber with a small threaded, metal piece at the bottom. When you tighten the bolts, the metal piece is pulled up, causing the rubber to expand against the toilet until it is tight. Kinda like a molly bolt. This works quite well.
Until, that is, you try to get them out. When you start to loosen the bolt after it's been in place for a year or two, the bolt sticks to the threaded metal piece and the rubber bushing nut is not tight enough to hold it still. So the rubber bushing starts spinning around and you get nowhere.
So grab the seat assembly near the bolt and pull up with one hand as you loosen the bolt with the other hand. Keep pulling up as you loosen. Alternate sides as you make a little progress. This puts pressure on the bushing, generally enough to hold it still while you unscrew. At some point you may have to work a pair of pliers around a recalcitrant busing to hold it still. But do so gently, maybe wrapping a little masking tape around the jaws of the pliers, so the bushing isn't torn up. If you get you fingers in there to hold it, all the better.
Before replacing, clean the bolt and bushing thoroughly, but do not use any petroleum-based lubricant, as that will quickly eat up the bushing.