And they were roommates... oh they were roommates. When Venti falls for his roommate, he pictures a beautiful romance - perhaps he confesses at a café, and they visit that same café every year to commemorate it. They'll go on cute dates, and take photos he'll treasure for eternity - just as he will Xiao. He didn't anticipate Xiao's guardian getting involved. (BAD ENDING DON'T READ IF YOU DON'T LIKE ANGST!)