Yep, downloadable. Only ten bucks, or 980yen on the Japanese shop (that's where I bought it). I just finished the game, took me about 8.5 hours. Totally rad from start to finish. You can choose English or Japanese language in the options.
I really recommend playing it on a New 3DS XL, the pixel art looks soooo nice in 240p, and the d-pad controls are great (no d-pad on a Switch).