Jeju Island
An island between South Korea and Japan, given up to a hive of mutant ants after the S-Rank Gate that opened there could not be cleared.
Jeju Island lies in the sea between South Korea and Japan and is the site of the worst gate disaster in Korean history in Solo Leveling. About four years before the main story opens, an S-Rank Gate spawns on the island, connected to a dungeon holding a hive of mutant ant magic beasts. The Korean Hunters Association mounts a mission to clear it and fails, the gate is left standing long enough to undergo a dungeon break, and the ants cross into the human world and take the island for themselves. The population is evacuated, two further attempts to retake Jeju come to nothing, and the Korean government sets the island aside rather than spend more hunters on it. Jeju is the only inhabited territory any nation has lost to a gate, and it is the reason Korea's hunting community is spoken of poorly abroad.
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