Sage Mode

Sage Mode is the result of using natural energy along with a ninja's normal chakra in perfect balance to explosively increase a ninja's abilities.

Usage
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Advantages

 * The user's physical strength, speed, stamina, and durability drastically increases.
 * The user's Ninjutsu, Genjutsu, and Taijutsu become more powerful.
 * The user can have the natural energy surrounding them become an extension of their body, increasing the reach of their attacks.
 * The user gains the ability to sense the chakra around them.

Weaknesses

 * Because the user is moving, the Sage chakra cannot be replenished, which means the user can't stay in this mode for extended periods of time.
 * In order to gather enough natural energy to initiate the transformation into Sage Mode, the user must remain perfectly still. Because of that, the user can be an easy target for an opponent.
 * After Sage Mode has ended, the user appears to experience exhaustion.
 * The two former weaknesses can be bypassed through the Sage Art: Amphibian Technique, where one Sage gathers chakra for another or as in Naruto's case, shadow clones can be used for the same purpose.

Imperfect Sage Mode
Jiraiya was not able to properly balance his own chakra with natural energy, resulting in him using an imperfect form of Sage Mode. So, whenever Jiraiya was using Sage Mode, he drew additional lines on his cheeks. Jiraiya would summon the two Toad Elders, Shima and Fukasaku to assist him in using Sage Mode. The Toad Elders fused to Jiraiya's shoulders with Sage Art: Amphibian Technique, gathering natural energy from their stationary positions for Jiraiya's use.

As a result of the toad-fusion (and the imperfect nature of his transformation), Jiraiya took a number of toad-like traits when using Sage Mode. His appearance was altered (he has a bigger nose, a goatee, and toad-like eyes). Further transformational attributes includes him taking on a toad-like stature, his hands and feet also became that of a toad and the lines on his face become much thicker, taking over each side of his face. Because of these traits, Jiraiya didn't like to use Sage Mode as it "displeases the ladies".

True Sage Mode
Unlike Jiraiya, Naruto is able to perfectly balance the natural energy with his own chakra. This allows him to use the true Sage Mode, which retains all of his usual physical characteristics except for toad-like eyes. A true sage would still suffer from the weaknesses of Sage Mode, requiring that they use Sage Art: Amphibian Technique in a battle situation. Because of the Nine-Tailed Demon Fox sealed within Naruto, however, Shima and Fukasaku were rejected whenever they tried to fuse with him.

As a workaround, Naruto has some of his shadow clones gather natural energy elsewhere while he fights. Once he has run out of his own senjutsu chakra, he has one of the clones disperse, giving him the clone's natural energy and allowing him to enter Sage Mode again. This method limits the maximum number of shadow clones that Naruto can create to five for as long as the clones are gathering natural energy, as anything more would interfere with their focus. To make sure he has enough shadow clones for use in battle, Naruto has only two shadow clones gather senjutsu chakra, allowing him to enter Sage Mode a total of three times. Naruto also stated that it is possible to lengthen the time he is in sage mode.

Nine-Tails Influence
During his meeting with Nagato, Naruto is stabbed in the gut with the former's chakra disruption blade. Nagato thinks he would be able to control Naruto with his own chakra, but Naruto inadvertently reveals a fusion of his Jinchūriki form and Sage Mode characteristics. The exact capabilities of this form are unknown, but it is enough to completely resist Nagato's control.