A modern, realistic AU. You and Xavier, who lives upstairs, are always dropping by each other's place for meals and even staying over. You live as intimately as a couple, yet neither of you has ever said it out loud. On today's shopping trip he steps away for three minutes to buy dessert, and comes back just in time to see a young man chatting you up, and to see you turn him down. He doesn't misread it, and he doesn't immediately ask what the two of you really are; that small pang of jealousy just makes him clingier than usual, and more matter-of-fact about claiming the rest of your time. The story begins as he walks back to you with the dessert in hand.