enjutsu (仙術, Sage Techniques) refers to a specialized field of jutsu that allows the user to sense and then gather the natural energy around a person. Senjutsu practitioners can then learn to draw the energy of nature inside of them blending it with their own chakra (created from spiritual and physical energy within the shinobi), adding a new dimension of power to the sage's chakra, resulting in the creation of "senjutsu chakra" (仙術チャクラ, senjutsu chakura). This chakra cannot be seen by anyone other than those who have been trained in senjutsu.
This new chakra enables the user to enter an empowered state called Sage Mode, which can then drastically increase the strength of all ninjutsu, genjutsu, and taijutsu. A person who is able to use senjutsu is called a sage (仙人, sennin). It would seem that it stems from the toads of Mount Myōboku, as only Shima, Fukasaku, Jiraiya and Naruto have been seen using it. Gamakichi and Gamabunta also seem to be familiar with it.
Sage Mode
Those who are able to learn to use senjutsu are able to enter a physical state called "Sage Mode". When active, Sage Mode increases the user's strength and speed, as well as more powerful jutsu.
Jiraiya had trouble using Sage Mode, as he slightly turns into a toad whenever he uses this form. This involved his nose and eyes (although the eyes can be excluded because as Fukasaku said the "toad eyes" are always present in Sage Mode being the sign of a true Sage) changing to a more toad-like appearance. Also, he grows a goatee just like Fukasaku's and his fingers and toes are toad-like. In order to use Sage mode in combat, Jiraiya relies on Fukasaku and Shima to gather natural energy for him.
However, Naruto, who has just learned how to sense natural energy and create sage chakra, only has reddish-orange pigment markings around his eyes and horizontal, golden slitted-pupils, showing his mastery over his Sage form. Naruto is able to use his Sage chakra very well, demonstrating the ability to lift a giant toad statue with his Sage chakra augmenting his physical strength soon after his induction to senjutsu. In order to use Sage mode in combat, Naruto uses shadow clones to gather natural energy for him and then has them disperse to transfer their natural energy to him.
Stats Booast
Speed: 30
Stamina: 25
Strength: 30
Agility: 25
Physical Endurance: 40
Chakra Reserves: 30 (plus ten per a post)
Chakra Control:30 (plus ten per post)