Anyone who knows even a little about Naruto understands that his ultimate goal as a teenager was to become the next Hokage, which means "Fire Shadow." The role as, effectively, village president was definitely a long shot for the seeming ne'er do well. However, it was also a hard-fought road littered with tragedy.
Naruto's ambition to become the Hokage reflected his mysterious parentage, as well as his desire for attention and approval from a village that hated him. It might also speak to Sarutobi. and how he failed to truly help the boy. Here's a look at the youth of Naruto and how it helped mold him into the Seventh Hokage.
Naruto's Tragic Childhood
Naruto Uzumaki was the son of Minato Namikaze, the Fourth Hokage of of the Hidden Leaf Village, and Kushina Uzumaki. His mother was the then-current host of the Nine-Tails, a powerful fox demon that was only kept at bay by her willpower. Unfortunately, during childbirth, Kushina was captured, and the Nine-Tails was released from her body, subsequently wreaking havoc on the village.
Both of Naruto's parents died in the ensuing carnage, with Minato sacrificing his life, and his soul, to seal half of the Nine-Tails in Naruto for containment. Unfortunately, the left the young Naruto an orphan and rob him of the privileges his parentage may have offered. His birth was a mysterious event kept from public knowledge. Naruto was given his mother's maiden name to maintain the ruse that he wasn't the son of the Fourth Hokage.
Sadly, it became public knowledge throughout the village that Naruto possessed the destructive Nine-Tails sealed inside of him. That caused the villagers to scorn and shun Naruto, treating the boy as a plague and, essentially, as if he were the demon itself. He survived on a small stipend supplied by a sort of welfare system, but it wasn't much.
Naruto had no real knowledge of who his parents were, or why he was shunned by the village. His own ignorance of the Nine-Tails stemmed from Hiruzen Sarutobi forbidding anyone to mention the creature. However, that attempt to keep children Naruto's age from hating him the way their parents didn backfired, because they shunned him just as much. But Sarutobi didn't seem to have much of a hand in raising Naruto -- he was barely around for his own children.
Naruto's Role as Hokage
Treated like an outcast by almost his entire village, Naruto resorted to pranks to get attention, no matter how negative. As he grew up, Naruto developed the desire to become the next Hokage of his village, the ultimate acknowledgment anyone could give him. Many mocked that dream, but the attention alone was likely satisfactory for the young Naruto.
His quest to become Hokage also may have reflected a sort of resentment toward Hiruzen Sarutobi, the Hokage before Naruto's father who took the role again after Minato's death. Naruto likely blamed him for not stopping the harsh treatment he received, and for not intervening when Naruto barely survived on government handouts. That's backed up by Naruto vandalizing images of Sarutobi early in the series. In the end, however, Naruto does respect the old man. Further, any resentment toward Sarutobi didn't prevent Naruto from being a sort of older brother to his grandson, Konohamaru.
In the end, all the harsh treatment Naruto received from villagers only made him more accepting and compassionate toward others. People who mocked and scorned him in the past are later counted among Naruto's friends. Thus, he becomes even more determined to become the next Hokage, eventually achieving this goal by the end of his series. Unfortunately, the role keeps him from being with his family as much as he would like, ironically echoing what Sarutobi went through. Still, Naruto is a just and powerful leader whose outlook on life is fueled by his less-than-happy upbringing.
The Day Naruto Became Hokage
Despite working tirelessly toward his goal throughout Naruto and Naruto Shippuden, the shinobi is never actually shown achieving the role Seventh Hokage in either of those series. Instead, fans had to wait until the 2016 release of the OVA The Day Naruto Became Hokage, included with the limited-edition DVD and Blu-ray of Boruto: The Naruto Movie. Episode 18 of Baruto: Naruto Next Generations, "A Day in the Life of the Uzumaki Family," also shows Naruto's ascension to Seventh Hokage (and includes flashbacks to the events of the OVA).
It's a little more difficult to pinpoint how old Naruto was when he became Hokage. However, the best estimates range from 25 years old to 31.