War is upon the superhero students of class 1-A, as the Paranormal Liberation Front, now lead by Shigaraki.
Though in a supporting role as the big heroes go in to keep them safe.
As the warplan unfolds, the superheroes will take the fight to two fronts. A team led by Endeavour and Mirko (where has this raging rabbit been hiding the first 5 seasons!) take on a hospital where the Nomus are being engineered, while a second team goes to the village infiltrated by Hawks that serves as the Front's HQ. In the ensuing battle at the villa, the series drops one of it's biggests death's and one that gave a very, very stomach turning ending as Twice is killed by Hawks.
As Hawks is in serious trouble against Dabi, enraged by the dead of Twice, the other group assaults the Nomu hospital. Mirko, at the cost of grave injuries, destroys Shigaraki's tank before he is "completed" but he jolts to life after all, while Mic discovers the identity of the Doctor who was experimenting there. His empowered Decay unleashed, many pro-heroes like Crust are killed in the ensuing chaos.
The heroes struggle on both fronts, with Bakugo and Deku jumping in to aid Endeavour. Meanwhile back at the villa, Gigantomachia awakens and goes on a rampage, bringing it down to classes 1 A and B to stop him. They try to hold him back, but as he is nearly defeated he evolves into an even bigger, berserk mode. At the other front in the meantime Shigaraki takes out Gran Torino and shoots Eraserhead with the quirk stealing bullet Overhaul developped in season 4.
He gets hit in the leg, but to prevent it from spreading amputates his own leg at the spot. With cities being evacuated as Gigantomachia rampages towards the battle, the others having been unable to stop him even though they delivered the anesthesiac succesfully. Shigaraki is being smashed up by Deku and the powers inside him from One for All, his body gets possessed by One for All who turns the tables. He strikes down Endeavour, and Bakugo jumps in front of Deku to prevent him from being impaled, taking the hits himself and be run through.
Both Shigaraki and Deku are transported to a realm within their respective, related quirks. In here, All for One tries to completely take control and steal One for All, but wielders of the quirk from the past step in to hold him back. As Deku reawakens, he sees Shigaraki fall to the ground, All for One telling him to run and recover. Toga ambushes Ochoca, wanting to find out why heroes killed Jin and if they would do the same to her.
Gigantomachia arrives at the field of battle, and Dabi reveals his true identity, the eldest son of Endeavour presumed dead for years. As he broadcasts his (manipulated as well) view to the world to shake the belief in the heroes, he attacks Endeavour. But at the final moment, the missing number 3 pro-hero Best Jeanist returns from being missing for months.
And he is not the only one to join the battle, as none other then Lemillion joins the fray, his powers returned thanks to Eri. With the balance slowly tipping back in the heroes favour, especially as Gigantomachia finally succumbs to a punch of Endeavour. With the League in peril, Mr Compress sacrifices himself to be captured at great injury to himself, in order to let the others escape. But as Spinner manages to awaken Shigaraki, he realises he has been taken over by All for One... and so comes an end to a very violent first arc of the season, where we had to say goodbye to heroes and villains alike (Midnight, nooooooooo ).
The second arc of the season, the so-called Dark Deku arc, faces the doubt that has crept both into the hero society, as well as that of the public into them. Shigaraki, now being used as an avatar body for All for One, leads the Nomu into the jailbreak of the high end security prison Tartarus, freeing not only his original body but also some high ranking villains like Stain and Overhaul from the previous seasons.
With the common people trying to take matters into own hands as they lost fate in hero society, the collateral damage grows even bigger while the students are still recovering. deku still hasn`t woken up from his injuries, while Shoto and his family meet with Endeavour in the hospital, joined by their mother. The backstory of the Todoroki family is laid bare, before they decide, together with Hawks and Best Jeanist, to team up and stop Shigaraki.
While hospitalized, Deku is faced in his dreams with the previous wielders of One for All. Able now to communicate with them, he learns more about the power, including that All Might was quirkless as well, and that he might well be the final wielder. He also gets told he needs to master the quirks of those before him as tools, and stop Shigaraki at all costs. Leaving UA, he secretly teams up with All Might, Best Jeanist, Hawks and Endeavour to stop the jailbreakers and hone his skills in order to prepare for the final confrontation.
As the final two predecessors of Deku decide to lend their powers as well inside One for All, Deku himself is ambushed by a former heroine turned hired gun, the ravishing Lady Nagant. Their fight is intense and he unlocks multiple powers inside One for All to finally overcome her, but in the battle he also learns that his beloved hero community has been build upon the blood of innocents.
Deku and the pro-heroes remain looking for All for One, but traps are riddled on their path. He is exhausted though, and when he is about to be overpowered his classmates arrive, who will be bringing him back to school where he will be protected as he recovers, yet he is unwilling to go. But the class engages him, culminating in bakugo even appologising for his behaviour in their youths, and bring Deku home to a fortified UA campus, though the civilians seeking shelter there are not happy to see the source of trouble amongst them.
Ochaka convinces them to have faith again in the heroes and grant Deku shelter to rest up before taking the fight back to All for One and Shigaraki. And All Might, he gets out of his being depressed feeling by non other then Hero-killer Stain himself, and calls in friends from all over the world, with the USA number 1 hero Star and Stripe already on the way to help out!
After a rather weak season 5, this arc greatly fired up the series again, being jam-packed of action from the get-go. This is without a doubt the best season of the series so far!