Valkyria Chronicle 3 never did get an official English translation, and likely never will as it was lucky to even be released at all in Japan. There's a nice unofficial fan translation by an anonymous team, however, which is linked below.
Sega appears to have *really* not wanted to spend any money on this game, as evidenced by the fact that the bulk of its maps are recycled from Valkyria 2 and it's the identical engine with almost nothing in the way of tweaks and pretty much all the same unit types. Even the new assets get a heck of a lot of mileage put on them over the course of the game, with only two or three static conversation panels for most of the characters. Within the limitations of the shoestring budget, however, the devs did about the best thing they could -- basically to rebuild Valkyria 2 and iron out pretty much all of its problems.
This one takes place prior to Valkyria 2, running roughly concurrent with the latter half of the first Valkyria game. We play as a penal squad called The Nameless, ostensibly a bunch of criminals sentenced to serve in the military taking on dangerous suicide missions, even though only like two or so actually look or act the part. They'll crisscross paths with the squad from Valkyria 1 here and there, even joining forces for a couple of missions. Encounters with the young teenage versions of some of the main cast of Valkyria 2 also occur.
The Valkyria game world is too firmly commited to its "PG" attitude to go anywhere really interesting or edgy with the idea of a bunch of criminals sentenced to a French Foreign Legion sort of deal, so there's no major tonal shift and you can expect the same general sort of Animu Tropes that the series has had to present. At least the obnoxious School Hijinx of the previous game are gone, though. Avan unfortunately shows up a couple of times as a guest unit, but he doesn't laugh. And you can pack his ass right back into the base anyway so you don't even have to look at him.
The main improvement Valk 3 makes is ditching the incredibly tedious grinding and item farming of the previous game. No longer are there Superbosses waiting to stall your progress out until you spend 30 hours grinding your characters up to the higher-tier classes. There are some challenging enemy commanders once in a while, but they're far from the almost-invincible state they were in in the previous game -- if all else fails parking the tank in their face and shelling them directly in the mouth three times in a row usually settles their hash.
Grinding is actually completely unnecessary. Each chapter has one optional side-map that you can repeat if you like, but every other main story mission can only be played once.
Surprisingly, even with the grinding cut and all the recycled assets, this is still quite a meaty game -- probably about 50 to 60 hours just to do the story missions and nothing else. I think it's actually the longest game I've played since Final Fantasy XII a few years back! Granted, you're seeing the same maps for a lot of this time, but at least some effort was made to freshen them up -- enemy and base placement changes each time, and some maps now have day/night modes and even varying weather conditions.
The only nitpick here is a few sudden unexpected rule changes that can ruin an entire map for you when they come out of nowhere. The amount of reinforcements that the enemy can spawn in just sort of increases at random unheralded points, for example. One of the bosses manifests a sudden ability to just appear on a map that you control at one point, and the rules about where a character has to be standing exactly to be considered "guarding" a base from enemy occupation are a little hinky and seem to vary from spot to spot. But on the whole, the game is pretty well-balanced, maybe even canting a little too easy. The only real bullshit map is the final one, which has some persnickety developments such that you'll probably have to waste 1-2 hours restarting it to learn about and anticipate them.
While the plot is still kind of on the juvenile side and the heavy re-use of maps is disappointing, the game's unique action-strategy hybrid style and alternate-universe Steampunk WWI setting are just strong enough to overcome and make the package as a whole quite enjoyable. More so if you've never played Valkyria 2, as then the maps here will be all-new to you! And even though it was a shoestring budget game, it certainly isn't lacking for playtime.