The summoning technique (Kuchiyose no Jutsu) is a common technique used by ninja in the Naruto universe in which a creature is instantly conjured upon performing the seals. Before using the summoning technique, a ninja have to make a contract to the clan of the type of animal they wish to be able to summon. This involves a signature with their own blood on a contract seal. This was shown when Naruto made a contract to be able to summon the Frog clans. Usually a ninja only has one summoning animal type but Nagato was able to summon a number of different animal types. Usually the animal type also stays the same throughout their respective lives but Sasuke proved it's possible to change the animal type. He was able to change from summong snake to a hawk. Summoning techniques also is not binded to summoning animals. They can also summon items or person. One method of using this jutsu is by sacrificing a little bit of your blood and using a hand sign and making a seal on a surface where the summon will appear. Another popular method is using a scroll to summon weapon items. Orochimaru uses some kind of special jutsu where he already has a seal in his arm where he just needs to rub his blood to be able to summon.
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