Rens Databook: Age/ World/ Ninja
AGE
Age is a shit show in the world of Naruto.
Traditionally it's implied based on the average academy entrance and graduating age of non bullshit ninja(Kakashi, Minato, Itachi, etc) that children in the world of Naruto attend the academy from the ages of 8-12 years old. With Kakashi being the biggest fuck you to every notion by graduating at 5.
The way he does that is by applying to the school early. Ninja hopefuls can apply for the academy at any age they please and well he's Kakashi so that's that.
Teuchi, the owner of Ichiraku Ramen, also seems to have opened his shop at either 12 or 13 years old. Based on the information provided in the official ninja databook.
All of this implies that in the world of Naruto you are a grown ass adult by the age of 12. That also means that everyone in the series seems to almost reach their maximum height by 12 years old with only a few exceptions growing afterwards(Mostly the men of the series and very few women). The only way to explain this phenomenon is that chakra subtly influences your growth rate.
That conclusion coming from the fact it's canon that older ninja use chakra to maintain a more youthful look. Essentially maintaining their bodies at their prime. Hashiramas era is supposed to be well into their 40's or 50's by the time Konoha is founded.
Main point being:
Age makes no sense.
Chakra likely accelerates growth to reach prime physical state and then decelerates growth to maintain prime form as long as possible.
WORLD
The ninja world is actually small in the overall scale of things. The ninja villages are supposed to only be a very small HIDDEN part of the much larger countries they reside in.
Lore wise at some point this version of Earth decided that having normal troops fight against the ridiculous superpowers that Ninja have was nothing but pointless bloodshed. In turn they made ninja become their exclusive military forces.
This means that the much larger world of Naruto is usually at peace with only ninja fighting and dying on a semi regular basis. So really it's more like a weird scenario where the governments in the MCU decided to disband their military and only engage each other with mutants or super people as their military force.
The main point:
This whole system honestly could just be to wipe out ninja in general and eventually carry on the world without them. To be fair Hashirama could have probably ruled the world if he wasn't such a "good" guy. So that conspiracy theory maybe spot on.
NINJA
Ninja in the world of Naruto aren't supposed to be as exciting as the anime and manga imply.
The point of the ninja is to actually be ninja aka stealthy unseen information gatherers and assassins. They all should be willing and able to kill, and are implied to have some semi loose morals on murder. The canon has many references to this being a fact.
Reality is that Naruto and a few other individuals don't follow their roles at all. Naruto in particular because, apart from his overall personality, also seems to be unwilling to kill. The only time he is ever depicted killing is at the start of shipudden, one single person in the whole series, and it's an implied kill not confirmed.
Setting him aside and the issue of ninja as the individual. The whole ninja system itself is actually extremely young. The American government is the youngest major government in existence and that is at maximum 245 years old. By the time Naruto begins his story Konoha is only about 78 years old. 78!
Main point:
The progression of the ninja village system becoming so central to the world is bananas and probably the most impressive show of political maneuvering that silently occurs in the background.
