Mega Man Star Force Dragon is one in a series of DS games based on the idea that a kid turns into Mega Man and plays card games to battle enemies. It's a combination of a very long, drawn out story with card battles.
The kid's name is Geo Stelar, and his father has vanished a few years ago in outer space. Geo has decided not to go to school, his mom is fine with that and she just heads off to work in the morning leaving him all alone. A man stops by saying "I was a co-worker of your father's. I stole these goggles from work, here have them." Suddenly Geo can see space aliens and energy lines, and the card battles against enemies begin.
Mega Man Star Force Dragon will be loved by some and not enjoyed by others so part of the challenge is figuring out which group you will fall into. There are several other games almost identical to this (Star Force Leo and Star Force Pegasus) so if you enjoy those, you'll like this one too. Your view of the card battle board is from over Mega Man's shoulder, so you dodge left and right to avoid blasts while figuring out which of your card attacks to launch down the row. It's a bit of strategy and timing mixed in together.
There's story to draw you in, too, although as you might tell from above I'm not overly fond of the message they're giving. The kid simply decides not to go to school. The mom says "Oh well" and abandons him all day. One of their teasing lines is in essence "stop whining like a girl." Like a Girl?? How about "stop pouting in your bedroom like a boy"?
It's also really tedious after a while to read long, long storylines three words at a time in the little scroll box. You have to click - click - click your way through hearing how to do things. They could have allowed the message box to take over the top area for example so you could read more easily and then return to the normal gameplay.
So if you're just out for fun card games, I'd recommend some of the MANY card games out there for the DS. There are lots of alternatives that have better graphics and gameplay. If you're a fan of the Mega Man series, though, this game provides exactly the same experience as the other ones do.