This is what I did about 25 years ago, for the same reasons that
MiyazakiHatesKojima
listed in the OP.
I had a PC with a 200Mhz Intel CPU, that had 16MB of memory. I found that it could emulate NES / SNES games pretty well although the emulation software was not nearly as refined as it is now. This is also when the internet was moving off of BBS systems and "web pages" were a new concept. (Anyway - I'm dating myself here!) Through searching for Final Fantasy info online after playing the original NES game and the most recently released Final Fantasy II, I discovered the II was actually IV and that there were two games that never made it to America. I also found out that Final Fantasy V had just been released in Japan. After some digging around, I was able to acquire ROMs of these games, but young me was stupid and didn't realize they were going to be in Japanese.
I spent that entire summer with scant resources - like physical resources, like books checked out from the library as even Google Translate wouldn't come around for another decade - pouring over the game and using context clues along with language clues to advance through the game. At first, I had to look up absolutely everything, but as time went on a lot of the language started falling into place. I played through all of the Final Fantasy games that America never saw until much later. I kept digging and found great games like Dragon Quest 5 and eventually 6. I kept at it for years and actually got pretty good with what I can only assume was a highly specialized subset of the language. A lot of the language skills I developed were pretty primitive because I never had to write it, never spoke it, or never heard it spoken aloud. My friends thought it was awesome as I would regale them with stories about these "hidden" video games.
However, after I moved off to college and real life hit it became something that I spent less and less time on, until I eventually stopped playing Japanese games all together (as later systems were more difficult to emulate or expensive to import). By the time I had the time and resources that I could devote to it again, globalization had happened and we have things like region-free game consoles and the overwhelming majority of Japan-only games I'm interested in playing getting western releases anyway. That being said, even after 25 years I can recognize enough to kinda/sorta get me by. I've been playing Dragon Quest Walk (like a Dragon Quest themed Pokemon Go) on my phone for a few months and my brain surprises me with stuff like "oh here is the item menu" even though a lot of stuff in that game has icons and such that make it easy enough to understand. There are still a lot of things I don't get and occasionally have to look up online though, like when they do game update announcements. My kids think it's cool now that I can just pick up something like that and know the language enough to just play it. So I've got that going for me, which is nice.