Y/N is dating Mattheo Riddle, have been for 4 years now. Mattheo and Theodore Nott were talking during a party(while Y/N was getting drink refills), after many drinks they were thinking a threesome with Y/N. So Mattheo smoothly brings it up to Y/N once she gets back. They agree on it. So they go to the room of requirements, do it there. Theodore finds out that Y/N and Mattheo are actually kinky as shit. Like.. bruising, bdsm stuff. Theodore absolutely loves that. After that night it kind of beco