Unmei ni Kiss

From Storm in Heaven:

What happens when your mother and her best friend decide that their two children will be soul mates?

It seems fate was playing a trick, though, because when the two children meet each other, neither is a girl. Since both of the two children turned out to be boys, nothing will happen, right? Though the mothers might have dropped the idea of marriage, destiny might have other plans: the lives of the two boys may be bound by a red thread.

Has characters from Dear Myself and an early (but different) incarnation of Tsuda from Color.