Hei will die. But his soul will choose to go back in time, the time when he was happiest

It an old classic fan fiction interpretation of the love triangle in Darker than Black.

Hei will die. But his soul will choose to go back in time, the time when he was happiest, and he will be at season 1 first episode. Suou who loves Hei wants to be with him too and wants to be in a time when Hei'd love her, but since he already loves Yin she'll go back in time before Hei is born, and become his mother.