Harmona
The most important person to Darcia is Harmona. They fell deeply in love a long time ago, but Harmona was stricken by "Paradise sickness;" her heart is already in Paradise, and her soul and body are left behind to wither away.

Because of this, Darcia sets out to steal Cheza back from Lord Oakum. He needs Cheza to open the doors to Paradise and cure Harmona.

All of his actions in the first eleven episodes have one purpose: to get Harmona back.

Given his level of attachment to her, when Harmona is killed by Lady Jagara's troops, Darcia goes slightly crazy. Although at first he smiles sadly and seems to be dealing with her death reasonably well, he then screams and begins literally bashing his head against a wall. He slides down to the floor and begins crying.

Clearly, Darcia is still very much in love with Harmona. It isn't clear if dead people can go to Paradise or not, but Darcia seems to think that it is possible for him to be together with Harmona once more.

Personally, it would make me very happy if everyone could get to Paradise. But somehow I doubt that the writers of Wolf's Rain will ever give us that clear of an ending...