Tough one. For Yu-Gi-Oh I'd say Kaiba and Mai. For GX I'd say Zane and Alexis. 5D's is Akiza and Crow. There's not many females that are main characters. >.< Who are your favs?
it would probably be more of either a sympathetic pairing because of the torment Marik endured, because being born of Marik's hate, Yami Marik in a way experienced all the pain Marik endured. or a falling for the kidnapper kinda thing, Or just a really messed up lust thing.
Sounds really nice and lovely. I do have to feel sorry for Marik. He didn't exactly get a chance to duel himself at all since Yami Marik was in his body.