This game has the best presentation in the entire jam. The aesthetics are a bit scattershot—a vaguely punk ninja protagonist, giant teddy bear enemies, a boss resembling a magical girl more than anything, old-timey film grain and music—but the individual elements are all well-made and fit together as well as, say, characters in the old He-Man cartoons. (Like, they're animated as if they belong in the same world, even if it's hard to imagine all these characters coexisting.)
The biggest problem is the simplicity and shortness. You basically just run forward and throw kunai; there's a jump, but it's too small to do anything (and of course you don't need it). There's not much in the game; you can beat it in about a minute. This wouldn't be as big a problem if you could play Indie Ninja in the browser, but for a nearly 300-MB download, I expect more.
I get that game jams give you a limited time frame to build things in, but I can't help but wonder if the time was well-spent. On one hand, part of me wishes less time was spent on making nice assets and more was spent on using them well. On the other hand, if the assets weren't so nice I wouldn't have such strong feelings about this game.
I'd say I want to see an expanded version of this game, but that would be a lie. There's not much to this game. What I want to see is the person who made this game do art for some game or another, possibly also staring the indie ninja. That could be neat.