Transformation Technique

The Transformation Technique allows the user to take the appearance of whatever they choose.

Overview
This technique is most often used to disguise the user as another person, but they can also turn into an animal, plant, or inanimate object; according to Sasuke Retsuden, inanimate objects are the most difficult to transform into, and users are shown familiarising themselves with an object's weight and feel before assuming its form. Users will gain the attributes and physical features of whatever they transform into, such as a weapon's sharpness or an animal's fangs. To be able to assume so many different forms makes this technique invaluable for not just combat, but intelligence gathering and diversionary tactics as well. In Sasuke Shinden, some transformations are shown to take some getting used to, such as if the assumed form has a different height than the user or if the assumed form wears clothes that the user isn't accustomed to.

Being able to use the Transformation Technique does not necessarily mean one can use it well. Ideally, the user's transformation should be indistinguishable from the original, so that if they were placed together they could not be told apart. Inexperienced users, particularly Academy students, will often have obvious discrepancies in their transformations, making them useless for deception. Even practised users, though their transformations may lack any serious flaws, can overlook small details of whoever they're impersonating (such as minor scrapes or blemishes), thus enabling careful observers to expose them as impostors. Even if a transformation is a perfect likeness, users can still inadvertently reveal themselves if they don't act the same way as their subject. Users can also be identified as fakes if their scent is wrong.

When a transformed user has been found out and attacked, they ordinarily allow the transformation to dispel. Some users may maintain the transformation in a final attempt to keep their cover, only dispelling the transformation once this effort fails. Still other users may, when they seem to be dispelling the transformation, actually take another transformation altogether, confusing opponents as to their true identity. Seemingly the only way to reliably find out if somebody is using the Transformation Technique is to knock them unconscious, which will cause the transformation to dissolve.

Tsunade uses the Transformation Technique to constantly appear several decades younger, keeping it active regardless of where she is or what she's doing. She only reverts to her original form when she no longer has the chakra to maintain her transformation. In the anime, Kagerō also keeps her Transformation Technique active for long periods of time, taking the form of a buck-toothed, hunchbacked man. In Akatsuki Hiden, the citizens of Shangri-la use the Transformation Technique at all times in a concerted effort to make new lives for themselves; their transformations only dispel when they die.

Trivia

 * Hensōjutsu was a real-life ninja skill, where the ninja would assume a false identity in order to blend in with a population and spy.
 * When Naruto Uzumaki transforms into a fūma shuriken, Sasuke Uchiha is able to tell that it's Naruto as soon as he grabs the shuriken.
 * In Naruto Shippūden the Movie, the Shadow Mirror Body Changing Method permanently changes the user's appearance, with no way to change back.
 * In Naruto the Movie: Blood Prison, Kazan earned the moniker "Hundred Transformations" due to his extensive usage of the Transformation Technique.