A person from one universe (of The Multiverse) falls in love with someone from an alternate universe. Or a Time Traveller falls for someone in the period he's visiting, or vice versa. The dilemma for the Time Traveller or dimension-hopper is how far to pursue the relationship: Maintaining such a relationship often means that one of the parties involved will have to give up his own life in his own [...] [tvtropes.org]