Many of his memories were altered, so even the people he knew, he doesn't remember them. And those who knew him, think he is dead.
Alright that’s still just as bad (if not worse) and my point still stands. The fact that they put him on psychoactive medication actually put him in danger because he is dependent on it to maintain his “normal state of mind” to the degree that he had an episode in the field that put him and everyone else in danger when he wasn’t able to take it for a couple days
So there are a couple of things I want you to consider here.
1- health & mind
Let's list a couple of things the MC would have to deal with right after waking up;
-The shock of having almost died
-Having to be frozen (dangerous/risky medical procedure)
-A whole decade passed (this one is huge, 10 years is A LOT of time)
-Numerous friends and family are now dead
-The apocalypse is in full force
Individually all of these scenarios can very easily cause a breakdown for someone and give them severe trauma and PTSD, let alone all piled on top of each other. Had they told him everything at once he would be at risk for a huge mental and emotional shock, that he may not be able to handle (he also comes from a very privileged background so there's a chance he's never had to deal with conflict/obstacles before). It's beneficial to ease the MC into the situation after having him settled and comfortable in a previously established routine. Therefore he can ground himself when needed (at least with a job and a paycheck, he has some sense of control in his life vs being told when you are most vulnerable in a hospital bed).
2- 10 years is A LOT of time and that alone has major impacts on people.
There are numerous studies on how those who serve in prison for 10, 20, or 30 years get out and struggle to function in society because everything completely changes in a small number of years (heck just think about all the tech and societal changes that came about through COVID, (almost no one deals in cash now)). These studies also delve into how these individuals feel they have to constantly play catch up, and that no matter how adapted they become, they often still feel like society and the world left them behind.
To put things in a better perspective
10 yrs ago-> the 1st Apple watch and wireless chargers were invented, Uber was a start-up, Peak Ebola outbreak
Whereas today-> tap/Apple Pay/contactless pay is the standard, most people have numerous wireless chargers and wireless headphones (air pods came out in 2016), Uber is known worldwide and used daily by many people (including as a food delivery service), etc
That's a HUGE tech shift and just a big shift in general day-to-day activities.
3- about his job and medical condition
His taking part in his job is probably beneficial as it gives him something else to focus on, especially being able to continue his job as a healer (also keep in mind the dad didn't want him to be a guide but MC insisted). I think because he had been a doctor before his incident, taking care of others helps put him at ease and being a guide gives him some aspect of his old life back. Also as I said earlier having a routine can help an individual be grounded during times of instability.
Finally, regarding his health condition and its effect on his work and the well-being of others, it would be treated the same way as any other medical condition. They monitored him for a period of time to make sure his health was up to standard, they did a primary health check and continue with follow up appointments to make sure that his health was maintained, they gave him mood stabilizers and additional medications to deal with any potential mood shifts or side effects you could experience from his condition. He and his doctors have done everything possible to maintain an appropriate level of health and therefore would be safe in a majority of lines of work. Furthermore, mood stabilizers are extremely common for a number of conditions and can be used in varying job sectors without any sort of issues. Keep in mind, it would be like any other medical issue where if an individual couldn't access their medication, there would be issues (diabetics would have the same issue, had someone stole their insulin-> the issue was not the condition but that someone stole another individuals medication, anyone would have negative side effects after missing multiple doses of their medication). Now if you want to argue that after that incident, that workplace would be considered unsafe for the MC (as his meds were stolen and little punishment was given), that's one thing, but the MC's condition isn't the safety issue here (unless it deteriorates).
Overall though I was rather impressed by the father and the secretary. I genuinely believe they wanted to slowly ease the MC into the truth with the least risk possible (they planned for a slow recovery) but I think the MC unexpectedly becoming a guide and getting picked up by the army just ruined their plans and kind of wrecked things. Though I don't believe withholding the truth for too long would be beneficial to the MC and could hurt him if withheld for too long, I also don't think telling him everything right away would have been appropriate as most people can only withstand so much pain and trauma before they break.
I definitely agree that Huiwon is in a complexly traumatic situation (along with the rest of the world) and that it’s important to pick how and where to break traumatic news, but my problem with it is that Huiwon is not in a protected bubble. He’s not amnesiac. What I’d someone mentions the current year? Like with the captain, he could meet someone he used to know which can trigger his memories. In the flashback it was revealed that he became a guide the day he was injured (and bitten), which is why the government was willing to spend so many resources on keeping him alive in the initial chaos. Medications aren’t always ideally effective, so he could start having flashbacks at any time. My issue is that this trauma is something that is impossible to keep secret forever, even if he doesn’t recover any memories. The sword is going to fall no matter what, but now there’s a risk of him breaking down in the field, which could put him and others at risk of injury or even death. It would have been better for them to let him recover slowly, and once he was in a stable mental place (while not working in a life threatening job) to break the news. Huiwon may be dealing with all these traumatic things besides the time jump, but he's in no way unstable from it. He’s not written as having severe nightmares, paranoia, hallucinations, mood swings, or any other serious symptoms which would indicate instability or serious mental problems. Of course everyone has their limits, but he knows about, and lives with every other traumatic thing besides this and is able to carry himself in a stable and relatively high functioning manner. He has the added bonus of thinking his father didn’t care enough to visit him even once after he woke up from a coma into an apocalypse. It’s just ridiculous to me that everyone assumes this is going to be the thing that shattered him when he deals with so many other even more traumatic things so effectively. So he can function with no major issues with a zombie apocalypse, catastrophic injury, death of his mother and (probably assumes most of his friends since he can’t reach any of them), believing his dad doesn’t give a shit about him since he refuses to visit, having to work in a demanding, potentially dangerous job that puts him close to the front lines (I know he technically had a choice, but it’s a personal moral obligation because not just anyone could do it if he refused), and almost dying during his job, but the time gap is going to be the one to do him in? Still doesn’t make sense. It might even be less traumatic for him than most because of the apocalypse. Everything was chaotic, it’s not like everything in his life was moving forward without him. The zombie apocalypse already subverted a lot of the aspects that are traumatic and difficult for long term coma patients. Difficulty adapting to a changed world? Already dealing with that in a big way. Alienation and loss of friends and family members? He thinks that everyone is either dead or don’t even care enough to call or pay him a single visit (other than the secretary). When he does find out, he’s going to have to deal with feeling betrayed by everyone who knew, and trust issue are sure to come with. Whether they wanted to ease him in or not, they should have broken it to him before sending him out into the world. It just seems like an irresponsible hill to die on because he will find out or figure it out eventually, but now there is no control of when or how he’ll find out, so it could happen when he’s in the field, throwing him off balance. I’m not saying the time jump isn’t traumatic, but it’s not something that can be hidden forever, so it’s better not to betray his trust by lying about something so important and let him process it in a safe environment rather that a random time from a random source.
So Huiwon was attacked by zombies, almost died, has now woken up in a post apocalyptic world, and now needs to work in high stress/potentially dangerous job to keep society safe, but they think the awareness of how many years he was in a coma is going to break his mind?! It’s so stupid that they are so obsessed with protecting him from this one specific trauma because there is so much of it coming from all directions. To keep this lie going, they need to keep him cut him off from everyone he knew, so he thinks his dad doesn’t care enough to even see him, and probably assumed that everyone else he knew that never reached out died in the initial and continuing crisis. No matter what, he’s going to find out eventually, but now he’s going to have the additional trauma of feeling betrayed and abandoned by the people he trusted (along with the medical gaslighting and unnecessary medications to suppress his memories). Hello trust issues. They’re making everything so much worse in the long run for essentially no benefit. It feels like a cheap plot forcer at this point. It would make more sense if they were trying to block severely traumatic memories that would prevent him from functioning/surviving, or if he somehow saw something classified/secret that would put him in danger for knowing.