So it only took around 5 years and 2 months but Umihara Kawase is finally available on Nintendo Switch!... On the Japanese Nintendo Switch Online service.
If you don't know it's pretty easy to get access to play games from the JP NSO apps, assuming you are already paying for an NSO subscription on your account that its region is set to somewhere outside of Japan, all you have to do is make a second Nintendo Account (I'm pretty sure you can't use the same email you used for your original Nintendo Account) and set that Nintendo Account region to Japan. You then make a second user profile on your Nintendo Switch and link the JP Nintendo Account to that second profile. You now have an account that can access the Japanese eShop which will allow you to download the NSO apps.
Because your Switch detects an account that is already paying for an NSO subscription, you do not need to pay for a Japanese version of the NSO subscription. Once you've downloaded the Super Famicom NSO app, you can access the app with your user profile, you do not need to use the Japanese user profile on your Switch to access it.
Now you can play Umihara Kawase on the Switch. What can you do differently on this game on the Switch compared to playing other versions?
1) Considering Umihara Kawase (SFC) never released outside Japan, you can now play the game with SNES controllers that were released for Nintendo Switch assuming you own one of them.
2) Rewind function: Playing any game on the NES/SNES NSO apps give you access to rewinding up to 30 seconds by pressing and holding the ZL and ZR button at the same time (those buttons are on the SNES controller for Switch). Since Umihara Kawase is the most difficult game in the series when it comes to its high rate of randomly spawning enemies, it's very useful to just rewind back a few seconds and avoid losing a life.
Could Umihara Kawase appear on the SNES NSO service outside Japan? Possibly. The fact that Panel de Pon got released on the NSO service outside Japan sets the precedent (especially considering that Nintendo of America in the past really screwed up the Panel de Pon IP thanks to putting the Tetris trademark on it in the West i.e. Tetris Attack).
Quite a surprise to see the original in gaming news today! Anything that brings the games to a wider audience is always going to be good news in my books.
I think it's a real shame that it's not available outside of Japan, though - there's so little Japanese text in the game (and an already-existing translation hack as a guide) that it seems silly not to bother, but localisation is a peculiarly expensive business even putting aside technical concerns, so I guess it's not a surprise.
Umihara Kawase recently came out on Japanese Switch VC in the Super Famicom section. It's the exact same game as the Super Famicom version, TNN logo and all. The only difference is its portable and has savestates, rewind, and the ability to change the controls, all of which come standard on Switch. I still feel the Vita version is better- it has a Field Select, it natively saves your high score and all your times (you need savestates to do that on Switch), and it's on a physical cartridge, where the Switch version is impermanent and digital. You can expect it to no longer exist shortly after the next Nintendo console comes out. In addition to that, I also feel that the Vita generally has the better Umihara Kawase games than the Switch does, but you probably already know that.
You can get it by starting a Japanese account (easy) and subscribing with your own local account, which covers all accounts for that particular Switch. If you only have a Japanese account, you can get yen by paying for online codes on import sellers like Play-Asia.
I'd still recommend the Vita version, but far more people have a Switch than a Vita or Vita TV, and the Switch version is still a pretty solid and cost-effective option.