Majin and the Forsaken Kingdom
Given that The Last Guardian isn't currently a thing that exists - and its gameplay mechanics are yet to be a matter of public record - it's tough to say whether Majin is just like it (although that's a fair guess). Perhaps a better analogy would be to Wind Waker's Earth Temple, in which you, the childlike hero, enlist the help of a magical friend to solve environment puzzles and defeat shadowy monsters. The biggest difference between the two is that while Medli was a nice enough little bird girl, Majin is a pretty big lug -- and yet, even friendlier!
The combat is pretty basic, though it looks like it'll become more complex as the game proceeds, with new abilities and level-ups. What's most interesting about fighting with Majin is that, whereas many games have you fight in real time while dumb AI helps you out, in Majin it feels like you're the one helping out the AI. Only he can finish off enemies to prevent them from respawning, and he has significantly more health and brute strength than you; so your job is to keep guys off his back, distract enemies with quick hits and dodges, give battle orders when necessary, and help execute combo attacks as the opportunities arise. The system is fun despite its simplicity, because it's really not about mashing the X button so much as it is about teamwork.
The non-combat gameplay is similarly simplistic but enjoyable, as you find things for Majin to break, or sneak around in order to hit levers, etc. that the big guy is simply too big to get to himself. All of this is polished up with bright graphics and cheery personalities (both in Majin and in the thief character) that straddle the line between lame and charming.
In short, the demo was fun. But it was a very brief cross-section of the game, that I'm not really sure is representative of what will come out next month. A lot of the retail product's success will rely on how well it balances the combat and platforming sections, and how it keeps both of them from becoming stale. And the end of the demo alluded to a boss fight, but that never happened, so who knows how that will turn out? Anyway, my ear's to the ground for this one.
Progress: Gave Up -- Finished the demo