Warning: This article contains SPOILERS for All of Us Are Dead.
Cheong-san should indeed return in season 2 of All of Us Are Dead, but only if he returns as a villain. Weeks after the zombie drama dominated the Netflix charts, all that's left for those who watched of All of Us Are Dead is to theorize about who and what they'd like to see in a second season. Names like On-jo, Nam-ra, and Su-hyeok are very likely to return if there is a season 2 of All of Us Are Dead, but there are also less likely names that viewers dream of seeing on the show once again.
Cheong-san's death at the end of season 1 was one of the saddest and most unexpected moments in All of Us Are Dead. The character had been one of the leads since the beginning of the show, and his relationship with On-jo was making for some of the most endearing moments on All of Us Are Dead. Cheong-san had also shown himself to be a skillful survivor, escaping the most dangerous situations and always willing to lead the students of class 2-5. The character's fate would however be sealed after his fight with Gwi-nam, in which the villain ended up becoming one of All of Us Are Dead's halfbies and from then on swore revenge on Cheong-san.
While Cheong-san's death felt very definitive — he was bitten and injured moments before he was blown up alongside the building — many viewers are certain that the character will return in season 2 of All of Us Are Dead as a halfbie. If that really happens, the best way for the show to bring Cheong-san back without diminishing the value of his death would be to make him a villain in season 2. Not only would this add an interesting new dynamic to the show, but it would also prevent the stakes in All of Us Are Dead from dropping majorly with such an important death being retconned.
It wouldn't be at all far-fetched to imagine that Cheong-san could return as a villain. The character has been shown to have a pretty fickle temper, which was intensified by all the losses he suffered during the All of Us Are Dead zombie apocalypse, and even fought Su-hyeok and Dae-su in moments of pure rage. Furthermore, it has been shown that although All of Us Are Dead's halfbies maintain their agency, they often struggle to keep their minds straight and have to deal with the constant desire for human flesh. That element added to Cheong-san's volatile temperament can result in a character who resents being left for dead and who can no longer be by the side of On-jo. Should a conflict between humans and halfbies actually happen in season 2 as it has been theorized, that could also put Cheong-san on a collision course with his friends.
The return of Cheong-san as a halfbie in season 2 of All of Us Are Dead is already being taken for granted by many, but the best route for the show to take would be bringing him as a troubled villain rather than a hero. That way, Cheong-san's return can be a bittersweet one and not lessen the emotional impact his death had. As scientist Byeong-chan said at the end of All of Us Are Dead: "It's easier to move on from those who are gone than to forget those who have changed."