In the main plot, both of them WILL end up with the MC, marry him, and STAY as friends. They have 100% Compatibility towards each other. The MCs relationship with Marie is like an Older Brother in his highschool days getting annoyed cause his spoiled younger sister keeps touching his stuff. Though in the official IF long side-story, Leon did went to the Marie route, and thats the one where Livia becomes miserable cause of the capture targets turning their attention to her, Livia and Angie not becoming friends, etc. I think thats what the Spanish guy was referring to man.