Haruto Sakaki is an 18-year-old Hunter working with the STN-J. He is brash, slightly hot-tempered, ambitious, and supportive. He often rushes into danger during hunts, and this often produces regrettable results. He is the newest member of the group after Robin, and is initially afraid of being replaced when she arrives. Sakaki is not biased about choosing friends however, and welcomes Robin to the crew. As with Amon, Sakaki does not show any superhuman ability. However, he is later hunted by Zaizen, suggesting that Sakaki is an unawakened "seed." He is saved via direct intervention of Robin, Amon, Doujima and Nagira. When that attack on Sakaki fails, they realized that Karasuma is left alone, presumed to be attacked and captured at the same time.

He later helps Robin infiltrate the Factory to save Karasuma, and provides covering fire while Michael attempts to get an elevator back online. He is confirmed alive after Factory's collapse, Michael mentions that he still hunts witches at the end of the series.