[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

 Seven and Luke share a look, confused. 


“He’s my soulmate, right?” His eyes fill with tears. “So what if I really can’t live without him?” 


Seven looks at him for a moment, before answering. 


“Vin… There are a lot of cases where soulmates decide to break apart. In most cases, of course, they stay together, because the connection is way too strong for people to ignore. But when the feelings come with it, it comes from the heart, not the soul.” 


Vince furrows his brows, trying to make sense of the words he just heard. 


“So can two soulmates be just friends?” 


“If they’re not in love, of course.” Seven nods. “I know of people who decided to stay as friends, because their connection was too strong even though they didn’t feel any romantic chemistry. It’s not that common, but I guess it’s just cause people don’t know how to separate all the different types of love there is, like Agape, that-“ 


Chapter XXIV