My Hero Academia has finally answered the question of how Best Jeanist convincingly faked his own death. Jeanist was retired as the no. 3 pro hero due to the crippling injuries he suffered battling All For One in the Battle of Kamino. That injured reserve status allowed Jeanist and No. 2 hero Hawks to work out a risky scheme: faking Jeanist's death to probe Hawks as an authentic villain. The play was key in getting a pro hero embedded inside the League of Villains' new Paranormal Liberation Front terrorist group, to provide key intel that helped win the war against the foes. But how did Jeanist play dead so well? Now we know..
Warning: My Hero Academia Chapter 299 SPOILERS Follow!
The new chapter of My Hero Academia is "Like Those Tragic Tales" and it tells things from the point of view of Hawks himself. After getting the pro hero's dark origin story in a dream flashback, we find him in a scene with Best Jeanist, following the war. Hawks is tracking down the loose end of who the informant was that sold out his true identity and dark family history to Dabi, and Jeanist is helping him investigate. During the drive, the two heroes have a chance to discuss recent events - like how, exactly, they convinced a cunning and sadistic psycho like Dabi that Hawks took out a fellow top pro hero.
Jeanist is explaining to the Hawks that if not for the achievements of Central Hospital in hero-saving medical tech, Hawks might have died from the injuries he received from Dabi's flames. In a ham-handed bit of exposition, Jeanist explains that Central Hospital also came up with the procedure that created the deathlike state he used to fool Dabi and Dr. Garaki - a procedure that was ironically based on the Nomu.
The ruse was very necessary: Dabi had Hawks brings Jeanist's body to him, for full identification. But the villain didn't burn the corpse - Dabi kept Hawks's corpse stored in a villain research facility, with plans to display him at a key point during the villains' terrorist campaign. Hawks's gambit paid off, as he was able to revive Jeanist, inside the facility, providing more intel for the heroes, and allowing Jeanist to arrive in perfect time to save the day in the war.