The toilets are out of this world, complete with seat warmers, built-in bidets, and music.
If you only ever go to Japan for one thing, go so you can experience the toilets. The next-level fixtures are not only hygienic (with front and back bidets) but most have heated seats and some have a built-in fan so you can use less TP. The best feature? The music function which you can use for "discretionary purposes" (or just for your own entertainment) while using the bathroom.