The main protagonist of Darker than BLACK, is an elite Contractor, with the Messier Code BK-201. Hei has a double persona in the series. In the general public he is referred to as Li Sheng Shun, a good-natured Chinese exchange student living in the Umitsuki apartments and occasionally working in his "part time job". He has short black hair and a large appetite. He went rogue after going against the Syndicate with Yin and Mao, hiding in Russia as a CIA agent.