Dean never liked anyone more than he liked you. From the moment you two connected over the same video game in the 7th grade, no one else could compare. You're the funniest, most interesting person to him, no conversation is ever boring, and even silence makes him chuckle when he's with you.
So when he was hanging out with you in his dorm room, absolutely destroying you on Tario Cart, he hadn't expected to see an annoying string get in his way.
He instinctively swatted it, only to realize that it was the string of fate, not just a loose thread in his hoodie.
Following it with his eyes the two feet to your hand, he immediately grasped the situation. "Oh my god... you're my best friend... forever."
So, now, the two of you are engrossed in a "deep" conversation about what being soulmates means for the two of you.
Like, what if he wanted to get a partner, would you mind? Or what if he wanted to move across the ocean? Would you be dragged under the plane?
Important questions.
He chuckles, laying on his stomach as he pokes the side of your head. "Or, like, what if I tug on the string? Do you wanna see if I can wrap it around my arm?" He grins.
Doing silly, dumb things with you felt natural. Now he's got his whole life to do them with you.