Warning: Spoilers ahead for My Hero Academia Chapter 299
My Hero Academia finally reveals how Best Jeanist returns to life after supposedly being done in by Hawks. In order to one-up the Paranormal Liberation Front, previously League of Villains, the Hero Public Safety Commission has tasked Hawks, the No. 2 hero, to infiltrate the League as a double agent. Having been groomed by the Hero Public Safety Commission into a master of deception and infiltration, Hawks has not only deceived the villains but the paragons of justice as well. Hawks eventually manages to singlehandedly expose the Paranormal Liberation Front and its plans, which leads to the Hero Association avoiding the worst possible scenario. Nevertheless, the raid still ends with a long list of casualties on both sides.
Hawks has gone to great lengths to prove his sincerity to the League of Villains. Not only does he has to turn his backs on his comrades, but he also has to fight a lonely battle. However, the biggest obstacle for him is his final task. Dabi tells Hawks to deliver Best Jeanist's - the No. 3 hero - body to him, which Hawks has executed to cement his identity as a new member of the league. Such an act has aroused a debate among fans whether or not Hawks actually did kill Best Jeanist.
In the series, however, Dabi confirms Best Jeanist's body despite having doubts about Hawks' allegiance. When the battle against the Paranormal Liberation Front was tipping towards the villains' side, Best Jeanist, alive and kicking, reappears, which posits the question "How?"
Chapter 299 of the manga shows Best Jeanist driving a sports car with a heavily injured Hawks in tow. Hawks injuries are so bad that Best Jeanist even jokes about being relieved that Hawks is merely sleeping and hasn't passed on yet. That's when he also reveals the trick behind his resurrection act. He explains that with the help of Central Hospital's genius medical technology inspired by the League of Villains' Nomu, they're able to induce a deathlike state. This is how they also managed to save Hawks despite his life-threatening injuries. This method, however, is not without side effects. Even after being "revived," the individual will feel worn out for a long period of time. In fact, Best Jeanist describes his condition as a worn-out denim.
As smart as Hawks' plan to put Best Jeanist into a deathlike state is, there are multiple ways it could have gone wrong. Given that the process takes inspiration from Nomu, there's a big chance the man behind the Nomus can figure out the trick. The chances of being caught only increases when Dabi demands for Best Jeanist's body to be identified. On the other hand, the League's decision of holding onto Best Jeanist's body leads to Hawks being able to revive him at the most opportune moment. With this revolutionary medical procedure, perhaps fewer My Hero Academia fan-favorite characters will cross the rainbow bridge.