The first Japanese game I ever played to completion with no knowledge of the language outside a few basic characters was Shining and the Darkness for the Sega Mega Drive, later localized as Shining in the Darkness for North America by Sega of America. It wasn’t mad savant skills that got me through this text-heavy role-playing game, but a spoiler-free walkthrough and plenty of maps yanked from a Japanese magazine that came with the game when I purchased it. I’d played a few Japanese MD games previously, but most were shooters such as Gaiares or not quite perfect arcade ports like Golden Axe or Altered Beast.
I stumbled upon Shining and six of seven other imports at a used book and record store in NYC back around early 1992 and couldn’t pass up buying all of the games at somewhere between eight and ten dollars each. All of those games are still in the library here and some even get pulled out and played on occasion. It took me the better part of the summer to complete SitD because I was only using the walkthrough when I got stuck and was filling in the plot on my own. It ended up being pretty close to what the actual game and English version would be because it was a simple “rescue the kidnapped princess!” story with a few expected and unexpected twists.
So, as 
"DESTROY ALL FANBOYS!" 