The main character in I-Ninja has a variety of acrobatic abilities that are used throughout the game to defeat the Ranx army led by Master O-Dor.[2] In addition to basic skills such as running and jumping, Ninja can also double jump, spin his sword around while midair for a limited time and use it to fall slower than normal, and use the shape of the environment to his advantage. Throughout the game there are several uniquely designed walls that Ninja can run on, and points where Ninja can use his grappling hook to swing across a gap.
Certain levels also provide Ninja with explosive darts and ricocheting shuriken to use against his foes; both of these can be aimed using a first-person view, but shuriken can also be thrown with an auto-aim feature. Occasionally, Ninja will encounter an enemy that will leap into the air with him (in anime fashion) to battle, and the two will remain suspended in a sort of flying void until the foe is defeated. While in this void, Ninja flies around and can dash, slash with his sword, perform an unblockable but heavily delayed thrusting attack, and throw shuriken if he has them. As Ninja attacks he will build an attack gauge that, when filled to certain levels, can be spent to temporarily enhance his abilities.
As the player progresses through the game he will gain access to more of these abilities; using them he can increase his strength, heal his life bar, ride a giant shuriken to quickly slay foes, or even become invincible, which allows him to greatly harm enemies in his vicinity without even touching them. When Ninja activates invincibility, he says "I-Ninja!", which provides the game with its namesake.