Why would Serge and Kid get married? Why wouldn't they? It's clear from the game they are in love with each other. To me, that's what Chrono Cross is: a love story. The thing is, once everything is said and done, we only get to see the beginning of their relationship, because by destroying the Time Devourer it was as if everything that happened throughout CC never actually occured. So, we see Kid/Schala standing there on what I assume to be Opassa Beach in a white dress (when I watched this again, it just all the sudden clicked to me that this was Kid/Schala, and not one or the other. The clue to me was the hair. Her hair is down like Schala, and yet she has a long ponytail like Kid. That sealed the deal for me), staring out into the ocean. So at the end of the game, we are at the beginning of Serge and Kid/Schala's relationship, despite everything they've gone through. It kinda works out funny that way, but I think it's great ;p Kato said something similar in an interview I read on this site, that Kid and Serge at the end of the game begin their "true journey" and that CC is an old fashioned "boy meets girl" story. So I don't think I'm far off when I say CC is a love story.