Everyone has a soulmate no matter if it a boy and boy, girl and girl, or a boy and girl. They have a mark on their body, to identify that they are soulmates. But if they are rejected, they turn black.
But there is a special kind of mark, a legand the God Mark. The God Mark hasn't been seen of billion of years. The parent have told storys about this mark, but the mark havn't been again after the first couple had them.
