The story focuses on Korea in an apocalyptic state, where many cities were destroyed, many survivors becoming unstable with cannibalistic tendencies or if not less sadistic. The concept of people turning into cannibalistic wild animals isn’t a bad idea, but the way it was used that idea is where the complaint comes from on my part; In the manhwa, nothing has been mentioned or seen that could justify their activities, it is not as if the series gave an explanation to the readers to help them better understand the progress that these characters had, perhaps an exception was their cannibalistic tendencies, due to the lack of resource that had inside the hole. But it’s a "perhaps" because in season 1 and episode 7, when Heyool went in search of first-aid to treat Haneul's wound, has been shown how these cannibals continue to eat human flesh even with the presence of wild dogs/insect and of canned foods: human bones were seen surrounding the pot they use for cooking and no traces of other animals; Furthermore, when one of them entered Heyool's lair, he prioritized the attempt to kill her than the resources found in that room.
Guess those wild people before were normal and ordinary people who had a drastic change because of the hole, but neither the protagonists and some secondary characters had that drastic switch, they still remained themselves even after surviving in the hole and returning to the surface; Unlike cannibals, in addition to not having any problem killing and eating humans, they also seem to only live off by instincts as if they were wild animals, as seen with their behaviors or when the main characters were attacked by them: season 1 and episode 3, season 1 and episode 7, season 1 and episode 8, season 1 and episode 9, or season 2 and episode 2. Giving the impression of that idea being used in a not so elaborate way due to the lack of explanation that there is about the drastic changes those characters had.
The constant use of going back to the past to explain certain situations helps to give context to some future situations, since there are events or topics where they cannot be explained without the use of flashbacks. An example would be the way Heyool was revived from the dead several times after being shot or killed by someone, but for the flashback focused on her, the meeting between her and Haneul on the stairs (season 2 and episode 16) could have ended more in a confusion rather than in a comforting moment; Going back to the past helps readers to better understand their high chance of survival due to the Reagent, when Haneul's father took care of her after dealing with the crazy couple in the hospital. Another example would be when it was explained how Haneul woke up "for the first time" after 2 months since the apocalyptic event, he mentioned about one of the effects of the Reagent being memory loss in season 2 and episode 16, something that has previously been seen to happen with Haneul: when he couldn’t remember who he was or what his name was (season 1 and episode 9) and then remember his name (season 1 and episode 15), same circumstance when he had temporarily forgotten about his current situation during season 2 and episode 3; explaining how Haneul woke up 2 months after the incident. Or helping to find out the reason that Haneul and Heyool were chasing Lee during his tours with his group of cannibals, giving the context in season 4 and episode 24 to help clarify the intentions behind the actions of these 2 teenagers.
In addition to solving some unanswered questions, it also gave development to the main characters: knowing more about their pasts, the before and after in the relationships with the people from their surroundings. Readers benefiting from flashbacks by helping them learn more about the characters before the current reality, for example: knowing Heyool's school lifestyle, being quite academic; the good and bad relationships with her classmates and her changes compared to the future, or showing the contrast in her way of thinking about her mother before and after the event; A similar story with Haneul, although not much of his school life has been seen, his cold demeanor with his father took a different path after the apocalypse. Although there are some flashbacks that doesn’t seem to be as relevant compared to others, visualizing the events of the past is a better option than letting the characters talk about the event; In season 2 and episode 11, it wasn’t necessary for them to teach the origin of the baby’s seizures and health problems, that could have been done in only dialogues but that wouldn’t have been so convincing without the visualizations.
There was a moment in the manhwa where it told 2 stories simultaneously, referring to when the protagonists had their respective focuses in the story: Haneul in search of Heyool, and Heyool's past. Initially it seemed that these 2 events were connected because: he saw a silhouette similar to her through the camera (season 2 and episode 8), he thought the voice he heard was hers, the shape of the panels being organized that made it seem as if the events were connected (season 2 and episode 11), or she heard someone calling her while he was calling her (season 2 and episode 12); But as the episodes went by, that connection began to be doubted and creating confusion due to the appearances of Heyool's deceased friends in season 2 and episode 11, and then readers realizing that these 2 events weren’t situated on the same timeline, also Haneul mentioned the gorilla seemed to be dead for a while and the clocks didn't match (season 2 and episode 10), along with his other mentions of Bitnara's sister and the doctor's body (season 2 and episodes 11-12). Creating confusion by the appearances of some characters, although perhaps that is the intention of the authors.
The manhwa has a setting that can attract the attention of readers, but there are some concepts that may not fit well in world building, or that seem contradictory to other concepts. In season 1 and episode 15, the officers are ordered to kill the remaining survivors of the area where the protagonists were, but then later it was mentioned the government was looking for someone with the tardigrade gene in season 3 and episode 9, giving the impression of being somewhat contradictory when establishing conflicting ideas due to how strange the setting is. In addition to that inside the hole, there were also similar situations where concepts could contradict each other: it’s not explained how there is an area with stored water located right next to the lava river, as can be seen in season 1 and episode 15; and if there is an explanation, then guess that Haneul being boiling in the water would have been part of the explanation because the water was really close to the lava; It’s also not known how Heyool managed to get Haneul out of that small crack, although it looked like somehow the crack was able to expand enough to get him out of there.
Other strange thoughts, although not necessarily a contradiction, it’s about the tigers and other wild animals roaming the areas. If those tigers were already there from the beginning based on the containers that were appearing in the flashbacks, how come the officers didn't notice them until when they were attacked? As if they were not aware of the animals roaming in those areas based on their reactions when they were attacked, although it may seem like an out of place situation since the government itself was the one who did that in the first place, perhaps that can be justified by saying only the people who asked for that order were the only ones who knew about it; initially being an event that came out of nowhere, although it did have a foreshadowing during the Heyool flashbacks (season 1 and episode 13) and Hanel’s flashback (season 3 and episode 14). Another doubt created by strange situations was during season 2 and episode 3, Haneul somehow managing to defeat a group of cannibals armed with knives with just using his fists can gives a strange sensation about the character; not too long ago he couldn't physically outmaneuver the cannibal with the chainsaw and if he couldn't do that in season 1 and episodes 3-4, how is it that he was able to defeat an entire group of them? Besides that he recently survived from a shot, perhaps he was still recovering from the shot, unless his wound has instantly regenerated like that time with the bar stuck in his torso; although perhaps that can be justified, maybe him gaining a greater strength might have been because of his superhuman abilities that he obtained due to the tardigrade gene.
It gets kind of repetitive about Haneul and Heyool having multiple fake kills in such a short time. In just the entire 15 episodes of the first season, Hanuel "died" about 2 times: when he was nailed by the tube (episode 6), and the supposed fall in the lava (episode 12); while Heyool having 1 "death": when Haneul believed she died upon seeing a corpse wearing the same uniform as her; then in the second season, the fake deaths became less frequent but they were still there: Haneul being shot in the torso of her (episode 15), and Heyool also being shot in the same episode. Making their future deaths or them being in dangerous situations not causing as much impact as in the beginning of the first season due to the constant use of that idea, in addition to also including the protagonists’ manifestations of their superhuman abilities during seasons 1 and 2.
Another curiosity is: in season 2 and episode 4, how is it that Bitnara wasn’t attacked by the gorilla but then she was attacked when she was reunited with Heyool? In season 2 and episode 8 demonstrated the animal’s aggressive behavior, where it tries to destroy anything it detects in it’s sight but that did not happen during its first appearance, although that can be explained by saying the cause was because Bitnara was speaking, as seen when she and Heyool were attacked by the animal after talking; But the gorilla should have still attacked Bitnara during its first appearance, the animal was right behind her when she was using the cell phone’s flashlight, and not only because of that but the gorilla seemed to be able to see in the dark because it could locate Heyool like in season 2 and episode 9. In season 2 and episode 12, it was somewhat rare that Bitnara developed a mentality similar to those doctors seeking a heart for their baby, she also wanted to seek a heart after her sister died, but she should already know at that age that her younger sister couldn’t be revived just by replacing her heart with someone else's. Or in season 1 and episode 10, how come the tiger survived in that place for 2 months? The area where it was locked up didn’t seem to have any type of food that would have helped the tiger survive those months, in addition to the fact that the door was locked and could not be opened without the code as it was shown in that same episode, and the only path that seemed to connect with the gate was the destroyed bridge, which may explain how the tiger got to that place by saying that it jumped off the bridge and onto the steep slope, but it doesn’t explain how the tiger handled the sulfur.
