It’s the middle of the summer and the city is facing its worst heat wave on record. When the air-conditioning unexpectedly gives out, Donghae and Hyukjae have to find some way to stay cool.

Mad scientist, Hyukjae, is on the brink of making a scientific breakthrough: time travel. But what he didn't expect was a boy from ancient times popping up in his lab. Heechul had warned him about screwing up the universe— maybe he should’ve listened.