Oni is an action game where the user can mix hand-to-hand combat with projectile weapons. The user takes control of Konoko, an agent of the Tech Crimes Task Force, as she fights through levels to find out about her past. The game is a third-person shooting and martial arts game where the user can switch from fighting with guns to hand-to-hand combat and vice-versa.
Oni features fourteen levels for the user to play through. When fighting enemies, the fight is not confined to one area. The user can fight throughout the level, like having the enemy chase Konoko from one area to another or have the enemy chase the character from the starting area of the level. When fighting hand-to-hand, the user can kick, punch, jump, and flip. Switching to weapons for range fighting or shooting enemies that are too far away to punch is allowed during combat. Players can unlock fighting combos as they progress through the levels. The user can find power-ups called Hyposprays to heal Konoko when wounded, or find invisibility gadgets to make the character undetectable to the game enemies. Weapons like rifles, hand guns, rocket launchers, and energy weapons are available to be found by the user. These power-ups can be found around the levels or on defeated enemies.
The enemies in the game are divided into strength levels and each enemy has their own style of fighting for the user to determine how to defeat.