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Kakashi's, Rin's and Obito's age
Alright folks, since there still seems to be disagreement regarding the age of those three, I'll explain it again, hopefully for the last time. All this information is based on the databooks and of course the manga, it also requires the ability to think logical. I won't take months and days into account, since we don't have enough of them. So only the years matter.
First of all, Kakashi's age:
- Kakashi is 30 years old. The Book of Sha is dated to 16 years past Naruto's birth (pNB), meaning that Kakashi was born 14 years before Naruto's birth (bNB).
- Kakashi became Genin at the age of 5, meaning 9 years bNB.
- Kakashi became Chūnin at the age of 6, meaning 8 years bNB.
We take a break here and look at when the 3NWW took place:
- According to the Book of Tō and chapter 239, it began over 10 years ago. The Book of Tō is dated to 13 years pNB, meaning that the 3NWW began at least 3 years pNB.
- Minato fought in the 3NWW, meaning it actually began bNB. But I doubt anyone would say otherwise.
- Itachi was traumatized by the 3NWW at the age of 4, meaning it happened 1 year bNB, since Itachi was born 5 years bNB.
So we have the war happening (and likely ending) 1 year before Naruto was born, with Kakashi being 13 years old. So far, so good. Now here's where most people make a mistake. They think Kakashi, Obito and Rin must be the same age, since they all graduated from the academy and became Chūnin at the same time.
To solve this, let's look at when Obito and Rin became Genin and Chūnin:
- Obito became Genin at the age of 9 and Chūnin at the age of 11.
- Rin became Genin at the age of 9 and Chūnin at the age of 11.
As you can see, both of them were 4 years older than Kakashi when they became Genin. But for them to be in the same Genin team after they graduated, they must've graduated at the same time. There's no example that would suggest it could be otherwise. Now, if Obito and Rin were four years older than Kakashi when they all graduated, it means that they were born four years earlier than Kakashi, amirite?
From this, we get the following:
- Obito is 34 years old, meaning he was born 18 years bNB.
- Rin would be 34 years old, meaning she was born 18 years bNB.
And now we conclude this:
- Obito "died" when he was 13 years old, according to the Book of Tō.
- When he was born 18 years bNB and died 13 years later, we get the date 5 years bNB for when the 3NWW happened, since Obito died in that war.
- Kakashi, who became Jōnin at that time, was born 14 years bNB and 14-5 is 9, meaning he was 9 years old when he became Jōnin.
Now we solved Kakashi's Jōnin age, when the 3NWW happened and how old Obito actually is (and Rin would be if she hadn't died).
On a sidenote, Minato told Obito that Kakashi's father died "five years ago", meaning he died 10 years bNB (5+5=10). Kakashi wasn't even Genin at that time, he was only 4 years old.