Naruto has a large number of characters, most of whom are ninjas. They initially study at the Ninja Academy, where the story begins, are split up into squads of three after their graduation and become Genin, rookie ninja. Each squad is assigned an experienced sensei. These core squads form a basis for the characters' interactions later in the series, where characters are chosen for missions for their team's strength and complementary skills; Naruto's squad 7 becomes the social frame where Naruto is acquainted with Sasuke Uchiha, Sakura Haruno, and their sensei Kakashi Hatake, forming the core of his world-in-the-making. The other three-man teams of his former classmates form another such layer, as Naruto connects with them to various degrees, learning of their motives, vulnerabilities, and aspirations. The groups of three are not limited to the comrades Naruto's age – groups in the story in general come in threes and multiples of three.In the Naruto world, countries operate as separate political entities ruled by landlords. Within these countries are hidden villages (隠れ里, kakurezato?), settlements housing ninja, warriors capable of using supernatural abilities in combat. A hidden village maintains the economy of the parent country by training ninja from a young age and using them to perform missions for other countries. The ninja of a hidden village also serve as the military force of their parent country. The leaders of the hidden villages hold equal status with the leaders of their respective countries. Five countries in the Naruto world—the Land of Earth, the Land of Fire, the Land of Lightning, the Land of Water, and the Land of Wind—are known as the "Five Great Shinobi Nations". These countries are the most powerful in the Naruto world. They are ruled by a feudal lord, and the leaders of the hidden villages in these countries hold the title of Kage. Other apparently smaller nations have been named in passing, in either the manga or anime, but are yet to be explored.
