Sage's Dream Series by Aki

Reguna, one of the last members of a dying-out clan of dream-seers known as 'Oracles', serves as a courtier of the childlike and (apparently) well-loved king of his country.One night, he has a prophetic dream of impending danger towards His Majesty - but is unable to discern the source of the threat. Determined to protect the young royal, Reguna then begins an investigation which takes him deep into the realm where dreams and political conspiracies intertwine...