Prologue is the recurrence of Jeon Jungkook's first love.
If there's someone who'd willingly trade his life for a wish to have someone's life back in a single snap, it would've been Jungkook who'd suffered mourning over a lost life.
Not expecting any of it to happen, the girl came to him in the same form but completely different characteristic, personality, interest and belief to only find out that she wasn't anymore the one he used to love.
She was completely the opposite, she was once what he believed an angel, but for her she's the employer of Satan from hell, her job is enough proof to it.