Last time I visited Japan (about four years ago!) mobile data was kind of a pain in the ass. I would rent a little mobile wifi hotspot. This time it looks like eSIMs are so well supported that I'm just going to use my phone.
That doesn't sound like a lot but it'll be huge. It means my partner and I can always be connected, even when we're off doing different things. Those hotspots run hot too (I guess the clue is in the name), so I always had to plug them into a battery, which meant I had to carry a bag (not enough pockets for all the things). This way I'll be able to enjoy my time there as if I live there again.