If they hear a sound or get a glimpse of the player character they become suspicious, displaying a question mark over their head and actively searching for the player character until they are convinced he is not actually present. They are also subject to terror tactics, and the player can learn to kill and display enemies in a terrifying manner, such as leaving a strangled enemy dangling from a perch or throwing a dead body at an unsuspecting live enemy, causing them to display an exclamation mark over their head, scream, stumble, and fire wildly at anything which scares or startles them. The player receives points for executing a variety of tactics such as silent kills, passing by enemies without being detected, successfully preventing the discovery of bodies, terrorizing opponents to cause them to fall into disarray, and achieving optional goals such as recovering artifacts and a series of haiku which tell the history of the ninja clan. This score is reduced when an alert is sounded by enemy guards. Depending on the player's performance on the stages, they earn honor and complete seals that are used to buy or upgrade skills and weapons and also unlock alternate costumes. Players get honor by reaching a specific score on each stage, collecting the secret scrolls, and completing the special objectives present in each stage. Some of the scrolls are obtained through secret challenges, where the player is transported to a room to solve a puzzle. Before each mission the player is taken to an upgrade screen, where they can spend their honor in three sections: Techniques (passive upgrades and skills such as new one-hit executions), Distraction Items (such as smoke bombs and firecrackers) and Attack Items (such as caltrops and poison-tipped darts). The next screen allows the player to select any unlocked costumes and equip items. Each costume (except the starting one) gives special bonuses, but also a side effect in order to balance its power, and must be unlocked by completing a number of seals in the form of optional goals related to the specialty of that costume (for instance, optionally terrorizing enemies in specific ways to unlock a costume which improves the ability to terrorize). Completing the game once unlocks a New Game Plus mode where the enemies behave more intelligently and can kill the player with only a single bullet or hand-to-hand strike, the player's line of sight is limited to a cone aimed in whatever direction the player is facing (preventing players from seeing what is behind, above, or below them unless they turn to look), the player is unable to see the enemy's line of sight and must intuit it from the direction an enemy's face is pointed, and the player can no longer detect the radius at which their actions will be heard by enemies.