Reincarnation of: Hiiragi.
Chronologically speaking, Daisuke started having the moon dreams first, as he started having them when he was seven (Rin recovered his memories at an even younger age, but at a later time, since Rin is much younger than Daisuke). Daisuke spends very little time on-panel in the manga, so not much is known about him. However, he does not trust Haruhiko, whom he believes to be Shion. He is also the only one who realizes the danger that collecting all of the passwords would pose, making it much more difficult for Rin to collect them all.