Of the all characters in Jujutsu Kaisen, Kento Nanami might be the most relatable to many older fans of the series. A former salaryman, he embodies the disenchantment with the adult world that many millennials experience after joining the workforce. He's blunt and doesn't really have an optimistic view on things, preferring realism over hopeful thinking that things will just work out. While he initially comes off as aloof and gloomy, he's really just a burned-out adult who's tired of the mundanity of being the lowest rung on the corporate ladder.
Nanami's outlook on life is the product of Japanese work culture. It isn't unusual for the younger members of a company (kouhai) to be asked to stay late and finish the work of their more experienced coworkers (senpai). Many of these kouhai are also tasked with getting projects done in a short amount of time, usually only a couple of weeks before the deadline. If they fail, their entire department may take the blame in the eyes of the higher-ups. On top of this, they are also expected to go out drinking with their coworkers and serve their senpai's drinks. While it's said to promote a healthy relationship between co-workers, it's also a lot unnecessary pressure.
In 2019, the average amount of hours for an employee was 50 hours a week. This type of environment has become so toxic that a word was created to describe when someone literally works themselves to death: "karoshi." Pair this with the average commute time of 39 minutes to and from work and it's easy to see why so many Japanese 20-somethings are disenchanted with the world. Young adults go into the workforce believing that they can make the world a better place only to have their dreams destroyed. Many of these people give up and become just another cog in the machine, but Nanami chose to fight this and try to do better. He ran away from becoming a sorcerer in the past, but came back to face his fears and prove that his life means something beyond the corporate meat-grinder.
Nanami decided that studying jujutsu was more logical than working a job where he was unhappy. Despite his apparent distaste for the work and those who do it, compared to working long hours as a faceless office drone, being a sorcerer is a step up for Nanami. To him, whether he'd stayed a salaryman or became a jujutsu sorcerer, the job would most likely kill him, so he might as well do something meaningful. Yet Nanami also values his time, and as soon as it's time to clock out, he checks out mentally -- something we've all done at one point in our lives.
Nanami's bleak outlook on life is the result of a culture that pushes people to give their all for a corporation that cares little for the individual. "The nail that sticks out gets hammered down" is a popular phrase that emphasizes how much individuality is looked down upon, so trying to make a change or do something impactful is out of the norm.
Nanami decided that his life and time were better placed doing something that could change lives, so he quit his normal job to become a sorcerer and try to actually do something meaningful with his life. He'd rather fight dangerous entities than become another statistic of Japan's work culture. He's representative of how fed up many people in their 20s are with how the world works against them and tries to suck them dry of their energy in order to continue a cycle of corporate toxicity.