[BL] Due to a rare condition, Vince’s end of the red string of fate is tied around his neck, while his soulmate's, Jack, is tied around his finger, like it’s supposed to be.

Theory says that if they "sleep" with someone that isn’t their soulmate, the string tightens on the other end, letting your soulmate know exactly what you are doing.
When Jack feels his string tightening, he feels heartbroken, and starts to sleep around with everybody as revenge, not knowing Vince was a victim of abuse.

When they finally meet, Vince is already suffocating.

or -
Love and fate's hopes for humanity were way too high and all they got was disappointment

Singularity: The Red String Around Your Neck

Theo’s breath gets caught on his throat, sudden realization hitting him. Everything Jack went though, and the things Vince’s mother told them... It all makes sense now, in the cruelest way possible. It explains the deep connection he felt between the two. 


"Yeah. I saw it, the string. Right before he..." Jack swallows dry, the words too bitter to leave his mouth. "I'm sure." 


"So you didn't get to talk to him about it?" 


"No, I- I couldn’t. Not that it matters. He's gonna hate me anyway." 


"Well, I hate me. I’m a horrible person." Jack bites his lip, refusing to cry in front of Theo. 


"Why do you want to talk to him, then?" 


Jack pauses and takes a deep breath. This is too hard. 


Theo looks at him and sighs sadly, shaking his head. He gets closer, resting his hand on his friend's back in an attempt to comfort him. He can feel his shaky breaths coming in and out. 


Chapter XIX