Most people make the mistake of thinking that sennin is a class of shinobi or something like a jounin, etc. Others think that it means to be a sage, a wise ninja made of experience and/or posses powers that far surpass others. If you think that, it is completly wrong There is the definition of sennin at this page: X Notice what it means to be a sennin: The Japanese term sennin is a loanword from Chinese xiānrén 仙人 "immortal person", known also as xian "immortal; transcendent; genie; mage; jdinn; sage; hermit" in Daoism. let's just skip "genie"; "mage", "jdinn", "sage". And we are left with 3 words:hermit, immortal, transcendent. We will take each word 1) Hermit For me it basically means someone who is very isolated and works alone. Or someone who have reached a certain point where they specialise in something that defines them. This could be true, but Jiraiya, Tsunade and Orochimaru travel a lot and have had a lot of contact with people. So the first half is gone. Second is also a no because they don't exactly specialise in only their definening traits, they do other things as well, so they don't only specialise in their summoned animal abilities. So they are not sennin. 2) Immortal The answer is obvious, though Orochimaru has, to a certain degree, gained immortality, he, Jiraiya, Tsunade were considered sennin before that. They might be the closest representation to what it looks like to be immortal(because they are famous worldwide and their power is as great as a kage), but they are just like other people, mortal. 3) Transcendent My guess is that this is the actual meaning to the title of sennin. It means someone who has gained a certain understanding of the world and everything around him. In a word, someone who has gained a Revelation or has reached a level of enlightenment, and have thus gained a power that is beyond human understanding. This is why the first Rin'negan user is considered a sennin. He transcendent the realm of normal human mind and used his unique trait to forge a new world. Naruto is slowly gaining this transcendent. So Naruto is becoming the first sennin since the begining of the ninja world. What do you think?