Even if the serial killer is the ML's father, it doesn't mean the ML & FL can't have a future together. Wouldn't they be able to stay in 1987 and have a life together? There hasn't been any clear explanation in the series so far that shows someone disappearing as a result of being killed in the past... and given that the male lead knows he dies the next year in the future, wouldn't it be safer for them to stay in the past?
Thank you so much!