The story.... makes no sense, but it all boils down to time travel, seriously. You play as Jiro Musashi, father of the legendary Joe Musashi(The hero from the first games), who during a invasion on his village gets sent into the future, for mysterious reasons, and must now battle Zeed in the future. The story never, ever makes much sense, and you do get cut-scenes before, and sometimes during, each level, but don't expect them to make much sense, at least you get to battle a mechanical shark!
Jiro has a couple of other tricks in his bag in order to make his journey easier, though not by a whole lot, in the form of four different spells and a parry. Y'see, blocking is too mainstream and a coward's move, instead Jiro can only parry, and you have to time it right unless you want to look like a fool and receive damage, although you can parry at, basically, any moment, and if you got your parry right, Jiro will automatically parry anything that tries to harm it soon after, meaning that enemy combos get parried automatically if you parry the first hit. As for spells, all of them are a one-time affair, unless you find a scroll lying about or respawn after death, and they provide many different bonuses, but lightning will be, by far, the most useful, making you invulnerable for three hits.
Platformers this hard need spot-on controls, and the game more or less provides. Controls are pretty tight, most of the time, but wall-jumps and double jumps could've used some tightening. Plenty of times you'll need to double jump out of a wall-jump, if you double jumped before the wall jump then you'll only be able to perform a single jump, the issue here is that unless you press the direction opposite of the wall, and jump, Jiro will double jump instead of wall-jumping, how is this annoying? If you double jumped before the wall jump, pressing jump will automatically perform the wall-jump, which can get confusing later on. Furthermore, movement is done with the analog stick, instead of the digital pad, which on a game played on a 2D plane isn't the best choice, when you need to fall down beneath the platform you are standing on, it can sometimes prove troublesome, due to the analog's stick nature. One thing to keep in mind, is that the hit boxes are a bit bigger than what you might expect. Hit detection is alright, but some projectiles have rather big hitboxes, so you'd better get used to them.
The game's worst aspect is, easily, its presentation. The game is fully 3D, but on a 2D plane, graphics are very lackluster and just plain looking. Still, the game manages to impress thanks to its setpieces. Y'see, the game never lets up, on the very first stage you'll go through a horseback section, then there's a section that takes place above a warplane, as enemies in jetpacks board your plane, how about the segment when you are on-board a truck and must go from truck to truck since missiles are targeting you, which sounds rather tame when compared to a mechanical shark trying to take a bite out of you while you are freefalling on a cascade.... only to be later fighting a chopper as another mechanical shark tries to destroy the solid magma you are running on.... the game is impossibly exciting and imaginative, specially for a 3DS game, easily making up for how lame it looks on a technical level. Cut-scenes between levels are made in a hand-drawn style that looks very cool, even if the animation itself is very lame. As for the music... it's very "ninja-like", very fitting, but not terribly exciting or memorable
Shinobi on the 3DS is a bit hard to recommend, not because it's bad, on the contrary it's really good, but because its target audience is rather small. If you are looking for oldschool games, this is what you want, but if you can't stand old platformers that require memorization, skip this one.
8.0 out of 10