I think he's made it pretty clear -- he wants to kill the Byouki and make Yurako his concubine. If he can do these things and save Mao's life, great! If not, too bad. Regardless, Mao cannot in any way trust him.
i think he simply want to destroy the clan and end this wretched system by any way possible. if it mean he has to be the winner of this death game, become next clan leader AND married to the successor line (hence yurako), so be it. that would explain all of his action.
I love that Daigo could actually fully cooperate, seal the spear with Mao, walk away, and I would still be like "this motherfucker is up to something and that was just another step in his grand plan."