I recently discovered that it's possible to play Dragon Quest X in english, sort of. Some enterprising fans have made two different programs that you can run at the same time as running DQX on your computer, one of them translating the menus, the other translation dialogue boxes in an overlay. The dialogue translation is done partially through a separate online machine translation tool, and partially with text translated by the fans. This of course means that the translation is far from perfect. There are plenty of gramatical confusion, obvious errors and general strangeness, and I imagine that a lot of the original script's subtleties may be lost. Still, I've managed to play through a fair bit of the beginning of the game, and I think I've generally understood the overarching story, and at least some of the character personalities (it helps that the characters a fairly expressive in cutscenes) through context. And I've rarely been confused about where I need to go next to progress the story (and if I do, there are some english-language faqs and walkthroughs available). It also helps that even though it's an MMORPG, there are several functions that seems to make it possible to play through most of it by yourself (including the ability to hire other player characters as NPC party members).
Setting it all up does require jumping through some hoops. First you of course need to register a Japanese Square Enix account and download the game, but fortunately the game has a fairly extensive free trial without time limits which you can play through
the entirety of A Realm Reborn and the award winning Heavensward expansion the whole Version 1 storyline and apparently a long way into Version 2. Then you'll need to set up a VPN if you're playing from outside Japan (though apparently this isn't required if you're playing from the USA?). I used ProtonVPN which was fairly easy (and free!) to set up, but there's probably plenty of other options. Once you've gotten the actual game running, you need to download the translation programs and do some setup, including registering an account for the separate "translation API". I did hestitate a little at this part, since the translation service requires you to type in a credit card number, even though it's free, apparently to make sure that the service isn't abused. It does seems fairly trusthworthy though, so I decided to risk it. When you have everything set up, you start DQX, and then the translation programs, and it all works fairly painlessly, though you might want to fiddle with the settings to get the translated text where you want it.
Fortunately, there are several guides (though some are a little outdated) for setting things up, and if you follow those (and occasionally make use of Google Translate when dealing with the Japanese Square Enix pages) I don't think it should be too difficult.
The translation tools are called
dqxclarity (menu translation) and
ahkmon (dialogue translation).
Here is a page with various links to guides for getting started.
Dragon Quest X Adventurer's Abbey has several guides on how register accounts and set everything up.
A guide I used for getting the game running.
There is
an english wiki with plenty of information about playing the game.
A walkthrough for the first part of the story.