Solo Leveling: Eternal Slumber, Explained

Highlights

The Eternal Sleep Disease is a consequence of the interdimensional Gates and renders victims permanently unconscious.
The disease drains victims of their life force and there is currently no known cure.
Jinwoo is able to cure his mother and his best friend's father using a powerful consumable called the Holy Water of Life.

The following contains spoilers for Solo Leveling Episode 3, "It's Like a Game", available on Crunchyroll. It also contains heavy spoilers for the Solo Leveling manhwa, available to read on Tapas.

In the third episode of Solo Leveling, Jinwoo's survival of the Cartenon Temple Double Dungeon is confirmed, and he recovers in hospital from the ordeal. One of the changes made to the sequence of events adapted from the first volume of the Solo Leveling manhwa by Chugong and DUBU is in the build-up to Jinwoo's use of the special Instance Dungeon key granted to him by the System. In the anime, Jinwoo first visits his comatose mother, Park Kyung Hye, before heading to the station.

Solo Leveling uses this as an opportunity to give context to his mother's condition: the Eternal Sleep Disease, which has left her in this unconscious state for nearly four years. What is the Eternal Sleep Disease in Solo Leveling, and what makes it significant to the development of the story?

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The Eternal Slumber is a Consequence of the Gates

Jinwoo Visits His Mother – Solo Leveling Episode 3

When the interdimensional Gates opened up across the world over ten years prior to the events of the anime, the well-explored consequence was the manifestation of magical abilities in humans, as well as the possibility of invasion from the magic beasts that inhabit the space beyond the Gates should they not be cleared within seven days. What the anime has been hinting at over the past three episodes is another effect of the Gates: the Eternal Slumber, or Eternal Sleep Disease in the anime. This supernatural disorder renders its sufferers permanently unconscious, and is a by-product of humanity's exposure to mana. One of Jinwoo's motivations for continuing with his work as a Hunter despite the countless times it has nearly gotten him killed is his mother's hospitalization.

With so little known about the intricacies of mana, its applications, and its effects, a cure for the Eternal Sleep Disease remains elusive.

Those who are intolerant to mana eventually develop this condition due to being exposed to a Hunter; a person who radiates mana. It begins with victims first losing consciousness for long periods before developing into the "great sleep" that it eventually becomes. What makes the Eternal Sleep Disease a major problem is that it drains victims of their life force, which is why they end up being hooked up to life support machines powered by essence stones. Such machines are extremely expensive, and due to the majority of people being unable to afford them, many people have succumbed to the condition. With so little known about the intricacies of mana, its applications, and its effects, a cure for the Eternal Sleep Disease remains elusive even in this technologically advanced, magically enhanced version of society presented in Solo Leveling.

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One of the major elements of the worldbuilding of Solo Leveling is that it is set in an alternate version of our reality, one with obvious metaphysical and ontological differences. The opening up of the Gates, and subsequent establishment of an economy around the Hunters is an aspect that has granted society various advantages when it comes to aspects like industry and also has the potential to completely upend the established international order. As Solo Leveling progresses, the political interests of various states becomes tied to their population of Hunters, and the overall strength of their Hunter forces.

Jinwoo Defeats Goblin – Solo Leveling Episode 3

Solo Leveling: Determination of the Weak

Jinwoo wakes up in hospital after the Double Dungeon ordeal, and discovers just how demanding and dangerous his new life as a Player can be.

The Eternal Sleep Disease hence presents an exploration into a more physiological consequence of the sudden arrival of magic and fantasy elements in a world that is otherwise just like reality. The fact that this intolerance to mana leads to the deaths of sufferers of the disease has Darwinian implications, especially with just how vast the physical differences can be between those who have awakened and those who have not, even if the comparison is between an E-Ranker and the average person. Those who are unable to live together with the magically-imbued lose their lives as if the current environment has selected against them, but normal humans are still the overwhelming majority.

There Are Two Known Sufferers of the Disease

Sung Jinah Visits Her Mother in Hospital – Solo Leveling Episode 2

Jinwoo's mother, Park Kyung Hye is probably the most notable sufferer of the Eternal Sleep Disease in Solo Leveling; however, later on in the story after Jinwoo has gained incredible strength, he winds up being able to find a cure. After clearing the 100 floors in the Demon Castle dungeon, which is a destroyed version of Seoul filled with hordes of demons and a number of archdemons, Jinwoo is able to synthesize a powerful consumable known as the Holy Water of Life, capable of curing any and all ailments. While it is an incredible item to have in his inventory, the recipe that he received for it can only create up to six potions, the first of which he uses on his mother, curing her of the Eternal Sleep Disease and all other ailments that may have arisen during her hospitalization.

The second time Jinwoo makes use of this miraculous cure is in the case of the second notable case of the disease: Jinwoo's best friend, Yoo Jinho's father, Yoo Myunghan, who develops symptoms of the disease due to his exposure to Jinho, who has a cameo in the first episode as he gets his rank appraised. After searching relentlessly for a cure despite doctors telling him of the futility of such a search, Mr. Yoo found out about the miraculous survival of Jinwoo's mother, and immediately set out to meet Jinwoo. Initially, Jinwoo was suspicious of him; however, after seeing how grief-stricken Jinho was when his father slipped into a coma, Jinwoo realized that the old man didn't have ulterior motives, making Yoo Myunghan only the second person in recorded history to recover from Eternal Sleep Disease.