He is a dark-skinned man with eyes the color of ice. He also has a near smirk on his face that was the result of nerve damage.
Miller did him a favor when he had the poor judgement to take pity on an unlicensed prostitute. Since then he and Miller trade favors.
When Miller's partner Dimitri Havelock, shows up at the Blue Frog having a bad night, Hasini gives Miller a call letting him know and that he would look after him for Miller.
When Miller was formally taken off the Julie Mao case, Miller got drunk at the Blue Frog. Hasini then drove Miller back to his hole.