Time travel was no common task, but after several months and years of reasearch and experimenting, Hybe Labs, South Korea's most prestigious company regarding quantum science, are finally prepaired to send their first test subject, a veteran from Busan, into the past. Jeon Jeongguk was prepared for this life threatening journey. What he wasn't prepared for, though, was to fall in love with a man that appeared in his high school history books.