Singularity: The Red String Around Your Neck

[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