Principia

In 2087, two disasters have shattered the established order on Earth. Tae-O, a janitor, lives on a small island formed from the sinking of a large city. One day, a mysterious intruder crash-lands, forcing him to team up with Ya-Na, his arch-enemy of ten years. Overnight, a camaraderie blossoms between Tae-O and Ya-Na, and they become increasingly embroiled in a series of incidents...

(Source: Naver, translated)