Ragnarok DS takes place in the same world as the popular Korean MMORPG Ragnarok Online. Developer GungHo Online Entertainment brings the same artstyle, job system, and fast-paced combat to the Nintendo DS, hoping to transfer some of Ragnarok Online's massive success to the DS platform. On the DS, Ragnarok DS brings players a single-player story and while the massively multiplayer aspect is not present, a 3-player co-op mode is included for Ragnarok fans who don't wish to adventure completely alone.
I never played Ragnarok Online, so I can't speak to how Ragnarok DS compares to it. GungHo, however, seems to have really tried to take advantage of the Nintendo DS capabilities, fully embracing the dual screens and touch controls. The UI is quite informative and functional with a party status window, text combat log, and minimap all on the top screen with the gameplay, skill/item hotbar, camera zoom button (you can view the game at three set distances - more on this later) and menu button on the bottom screen. The game is best played using only the stylus, dragging it across the screen to guide your character around and tapping a skill on your hotbar then performing the various tap-and-hold or slash commands to execute said skill.
The game has a robust class/job system, featuring a novice job (the starter job), seven "low level" jobs (requires level 10 in novice to choose a low level job), seven "high level" jobs (each low level job graduates into a specific high level job at level 30), and two special classes that are only unlocked after fulfilling certain conditions. Each time you level up your job level you get a skill point that you can allocate to a skill of your choice. You also have a base level; every time you level your base level up you get statistic points to allocate to the stats of your choice. The level requirements might sound like a pain, but you level fairly quickly which ensures you have plenty of different skills to play with.
Further customization can be found in the equipment department. Armor and weapons you find can have a random number of card slots (0-3 slots). Enemies you fight have a chance to drop a card specific to that enemy type with various statistics which you can then put into your gear. There is also a blacksmith in towns where you can modify your gear to make it more powerful. There is also an assortment of hats that appear to have a smaller drop rate than regular gear. From what I've heard, headgear was a much revered aesthetic factor in Ragnarok Online, and GungHo brings the cutesy hats to Ragnarok DS full force, complete with silly looking wizard hats and bandanas.
As far as how the game looks, sounds, and plays, the graphics are both cute and charming and look surprisingly good for an anime-style DS game - IF you're zoomed all the way in. The problem is that it's very impractical to play at the maximum zoomed-in camera view because you simply cannot see enough of your surroundings to navigate around or even fight very well (especially if you're playing a ranged job). When you zoom out, as you're forced to do almost all the time, the characters and enemies lose their crisp graphics and definition which makes the game look disappointingly worse. The music fits in well with the game (I believe a lot of the soundtrack was taken from Ragnarok Online if I'm not mistaken), but the tunes of the different songs suffer from being usually only a few bars long and then repeating over and over which can become tiresome.
The single-player campaign has an extremely generic storyline, the same kind of outline countless JRPGs have visited time and time again. The main character, Ales, has just been orphaned upon the death of his mother. He blames himself for not being strong enough to save her and thus decides to become an adventurer so he can learn how to become stronger. He immediately finds a girl named Sierra washed up on the beach with a past so tragic it gave her amnesia. Shortly after meeting they decide to go on grand adventures together. The single-player is entertaining enough, and it has few nice touchs. The party companion AI is pretty good, for one (you do not control your party companions as combat is in real-time). On the other hand, it also suffers from a couple of glaringly bad design decisions. First, in each new area you must find the map to get the minimap of that area to display on the top screen. Now, I know that many games employ a system like this, but the reason it's especially such a poor decision in Ragnarok DS is because the amount of environment you can see on the playscreen is so small (even zoomed all the way out) it becomes almost vital to have the map to navigate the maze-like zones. In a couple of areas where I missed the map, I found myself walking around in circles for a frustrating amount of time. I simply don't see why this design choice was made. The other major frustration factor is that after completing a main objective in the main quest (which almost always has you crossing several large zones), you must trek all the way back to town to get the next step. This seems like nothing more than an annoying time sink as nothing ever happens on the way back to town. The developers could have simply ported you back to town upon completion to the exact same effect with the only things missing being your lost time and irritation.