Help me out here, I see a lot of hype for this game on forums etc, but I honestly have no idea why. Can someone explain?
Why ask why? Ask why not!
...In all seriousness, though, what is it you don't understand? Your question is a bit broad, which makes it hard to answer. Are you approaching this from the "it's clearly a pandering fanservice game, so why are people championing it?" angle that a lot of media outlets have taken, or from the "it looks like just another anime-inspired JRPG, so what sets it apart?" angle?
Or is this more of a general "tell me what makes this game good" request?
In any of these three cases, the answer will boil down to "it's an envelope-pushing satire RPG with an irreverent sense of humor, a unique setting based very accurately on a real-life location, gameplay that centers very heavily on customization and silly experimentation, and a story that's surprisingly nuanced and well-written with characters who are quirky, charming and generally all-around likeable."
But that brief explanation can be expanded upon quite differently depending on your angle.
-Tom