3:40 layover in HND. What to do? Business class so will have lounge. To clarify it's T3 to T3, so minimal transit distance. I heard to eat at the eel restaurant?

I've been to Tokyo about half a dozen times, and if I had more time I'd probably slip out, but is there anything even possible to do outside in that short amount of time? I'm also OK sitting at the airport/lounge to relax/shower/eat.

Is the airport garden worth going out for?