I'll be honest: When I first saw this video I thought it might be fake, largely because the Mario model in between the game footage is atrociously animated, and the box art consists of the same stock pictures we've been seeing since the regular DS era.
But since it's apparently real, count me on board. This game looks fun as heck, and it's as close as I'm ever gonna get to a Mario RPG where you can recruit baddies to your team.