okay, but yandere swap!spamton.. what would he be like..? *sweats*
Instead of just wanting you, he needs you. His behavior is even more erratic. He tries to introduce himself to you in a romantic way, presenting himself as a handsome stranger that you happened to meet who's already infatuated with you after just a few meetings, but, he doesn't pull it off well. After the first five or so encounters, you start getting hints that he's not very stable. If you brush it off, and figure that it's just because he's lonely and eccentric, congrats! Eventually, he presents himself as the perfect boyfriend, and nothing ever seems wrong.
If you seem unnerved, though.. he starts to panic. He's not a good actor. And he doesn't plan. His visits get more obsessive, more frequent. Oddly specific gifts from him begin to show up.
Most likely eventually ends up with you locking yourself in your bathroom or bedroom with him banging on the door, screeching with ten different voices at once with a dial up tone in the background. Eventually, he stops, and the persona comes back. He busts open the door, but calmly looks down at you, holding out his latest gift. It's clear from the threatening air around him you don't have a choice.