(Inspired by @Pepethehuman)
Everyone in existence is born with a delicate and light String. There are many different colors to the strings, bringing strange and mysterious effects to the person it is bound to. At the end of each thread is a person, connecting two separate people together.
They are considered SOULMATES, two people bound by the workings of FATE.
Though, it's FATE which is controlled by the SOULMATES.