The world of superheroing has changed forever, because the Symbol of Peace has stepped down into retirement… and his successor isn’t really ready to take up his mantle. In fact, Izuku Midoriya is only just entering the world of professional superheroes, and he has a lot to learn.

And he jumps into the deep end in “My Hero Academia Season Four Volume One,” which follows a handful of the Class 1-A students onto Hero Work Studies. No, not like their last internships — these ones take them right into the thick of superhero action, while also introducing a sinister new enemy with a very different kind of evil plan. And, you know, a colorful array of new superhero characters.

Izuku becomes determined to do his Hero Work Studies internship with Sir Nighteye, the straitlaced and grim former sidekick of All Might. Unfortunately, Nighteye has a personal dislike of Midoriya, believing that he is an unworthy successor for All Might; though he allows the boy to join his agency as an intern, he is still convinced that the talented and disciplined Mirio is the right kid for the job.

This puts Izuku in the middle of Nighteye’s investigation into the Shie Hassaikai, a yakuza organization run by the sinister Overhaul — and it becomes personal when he stumbles across a small girl named Eri, whom Overhaul is keeping captive. At the same time, Kirishima encounters bullets that can temporarily erase people’s quirks, which Nighteye believes are connected to the Shie Hassaikai and the little girl.

This investigation leads to a massive team-up of heroes and their interns — including Izuku, Ochaco, Asui, Kirishima and the Big Three — attempting to take down the Shie Hassaikai and rescue Eri. But they find that Overhaul is prepared for their attack, with the vicious Eight Precepts of Death ready to kill anyone who tries to stop their master. And that’s not even taking into consideration that Overhaul is ridiculously powerful himself, or that he has a connection to the League of Villains.

Just a warning: if you’re a big fan of the Class 1-A students other than Izuku, Ochaco, Asui or Kirishima, you’re not going to have much of your favorites this half-season. It focuses far less on school-related antics and more on professional superheroing with actual pros, which gets moderately dark, graphic and violent. You can tell things are going to get nasty when Overload casually liquefies someone’s upper body (and no, I won’t say whose).

The first half of the arc is a relatively slow burn, balancing between the mundane detective work the heroes are doing and the complicated relationships between All Might, Midoriya and Nighteye. And once the infiltration starts, the series goes full shonen, focusing on a series of fights between Overload’s powerful goons and the various heroes and teenagers. Lots of punching, lots of blood, lots of giant octopus tentacles, lots of weird wibbling wobbling corridors.

Izuku also has to face some personal obstacles in this arc, discovering that Nighteye dislikes him as the One For All holder, and wants him to fail. This also leads to some friction with All Might, and the discovery that his mentor has been keeping a dark secret about himself. Kirishima also experiences some growth as a character, as we see him struggling to use his abilities to fight villains, even as we see what spurs him on to be a hero despite his lack of a flashy Quirk.

And there are a number of smaller stories being juggled — Sir Nighteye’s tragic fallout with All Might and the present distance between the two men, Mirio’s conflict with Overhaul to save Eri, the presence of the friendly and orb-shaped Fatgum, and Tamaki’s struggle to overcome his crippling social awkwardness and turn his Quirk into a devastating power. You know he’s a brilliant hero when he can take on three powerful Quirk users at the same time.

Compared to the arcs that came before, “My Hero Academia Season Four Volume One” is focused less on school and more on the dark and bloody business of pro superheroing. A great balance of powerful emotion and explosive action.