A Red Gate is a special gate that completely seals off its entrance once humans pass through it.
Aside from its red color, a Red Gate differs from a normal gate in that it seals off its entrance once someone walks through it, trapping the humans already inside the gate and preventing anyone else from the outside from entering the gate, and refuses to open until one of three things happen: the boss is defeated, the entire raid party is killed, or a dungeon break occurs. The minimum difficulty level of a Red Gate is also at least B-Rank, meaning that the hunters within the gate are doomed if there isn't at least one A-Rank among them.
The environment within a Red Gate is also usually very harsh and ranges from a scorching hot desert to a freezing snowy field. As a result, aside from the chance that they might get killed by the monsters in the dungeon, the hunters within the gate also face the additional possibility of dying from environmental factors such as frostbite, heatstroke, or starvation, making Red Gates much more dangerous compared to normal B-Rank or A-Rank gates. Time is also dilated within Red Gates, to the point that one day inside a Red Gate equals one hour back in the human world.
Despite how unusually dangerous they are, however, Red Gates are impossible to predict, as they initially appear to be normal blue-colored gates and only reveal their true nature after humans pass through them. They also stop radiating mana after closing up, preventing their mana levels from being accurately measured from that point on.
In his attempt to expose Han Song-Yi to the dangerous reality of being a hunter, Jinwoo reached out to his contacts in the White Tiger Guild and managed to get both her and himself slotted in one of the guild's training exercises. Unfortunately, things went horribly wrong when the gate they walked into turned out to be a Red Gate, stranding them on a freezing, snow-covered landscape.
Due to the poor long-term decisions made by Kim Chul, the raid party leader, eight of the hunters who went through the gate were either killed by the monsters within the dungeon or by environmental factors such as frostbite or starvation. Chul himself was later murdered by Jinwoo when he went violently insane and attacked the low-ranking hunters who had remained behind in the forest. As a result, out of the twelve members of the guild who went through the gate, only three came back alive.
Several days after the events of the Jeju Island Raid, a B-Rank Gate suddenly spawned in the middle of a highway in Seoul. Due to the fact that his guild office was based nearby, Jinwoo was tasked by Go Gunhee, the Chairman of the Korean Hunters Association, with taking care of the gate. Although the gate later revealed itself to be a Red Gate, Jinwoo was able to clear it almost effortlessly and returned back to the human world after only spending a few hours inside the gate.