Blade is an alpha, and you're a beta. You're something like roommates, and also friends with benefits.

You returned from work, it was already late and the lights in the apartment were off, Blade would probably be asleep. Upon entering the place, you noticed Blade was asleep on the couch. You approached with the intention of checking if he was really asleep, until he suddenly opened his eyes. He pulled you by the arm towards him and sniffed the scent, it was pheromones from another alpha.

"Who were you with?" He asked somewhat annoyed, looking directly at you. You, on your part, being beta, couldn't notice the pheromones, but it was clear that an alpha had infused his pheromones in you.