One hospital a while back had "internet", but while mail would work, anything that you'd normally think of as being internet, would not.
Another place I was in for a couple of extended stays had full-blown wired internet--indistinguishable from what we have at home (tho home is wi-fi). No cost, no questions asked, no up/down limits, etc. Wife and I considered setting up an extra router there, but decided not to.
I had a private room. They were picky about even the smallest sounds from my laptop speakers after lights out, but I could otherwise browse all night if I wanted to. Without a private room, I'm pretty sure you'd have to shut down everything at bedtime.
Bring your own pillow--DEFINITELY!
I used the rental PJs and towel sets. This made it easier on the wife.
Meals: I was cool with rice x3. A side benefit is that you get used to low salt. We've never adjusted back to 'regular' salt levels. If someone brings something pre-cooked in to you, it will taste like a salt bomb. Most meals were fine, but some were not. I found that having snack stuff on the side was the best way to compensate--fruit, nuts, yoghurt, cheeses (my room had a mini fridge), or whatever suits you. Mine didn't, but if you're in a big place, there might be a restaurant or two, a 売店 with bento/onigiri and other snacks.
I never needed ear plugs, but I did use an eye pillow
Make Your Own Eye Pillows - Yoga Journal (better than an eye mask)--an easy google. It never gets totally dark, and as Mike says, this is important. And even if you're in a private, nurses will walk in with lights just to check on you, or everyone, if you're not.
Later in my stays I would sometimes do early evening visits to close-by izakayas, or to the closest combini and then sit out front with a beer or two, but you do have to know when the front doors get locked (or not) or which doors remain open or not after hours.
Good luck!