Sennin mode

Sage mode is an senjutsu(sage techniques).It is introduced during second part of the series that is taught from summons who obtained the title of sage.Naruto achieve senjutsu by combining his chakra wirh "natures energy".Those who master senjutsu are able to enter a state called "sage mode" where they adopts the physical features of his animal mentor.In this series Naruto and Jiraya obtained sage mode from the great toad sage, Jugo's bloodline.