(黒崎 密,Kurosaki Hisoka?), voiced by Liam O'Brien (English), and Mayumi Asano (Japanese) is a 16-year-old Shinigami and Tsuzuki's current partner. He possesses strong empathy, which allows him to feel the emotions of others, read thoughts, see memories, and pick up imprints of clairvoyance off inanimate objects.
He came from a tradition-oriented family, and he was trained in traditional Japanese martial arts. His parents were afraid of his spiritual powers, which they considered unfit for their heir as well as something that could unfurl the familiar secret; so as a child he was often locked in a cellar when caught using his empathy, they often considered him a monster for it. Though it's unknown if they felt guilty and sad or even felt regret for what they did to him after he died.
When he was 13 years old he went out under the sakura trees near his home and stumbled across Muraki in the process of murdering an unknown woman. In order to keep him from exposing the crime, Muraki tortured Hisoka (the anime shows non-graphic rape) and cursed him to a slow death that gradually drained his life over three years. The curse is still active after his death, and visible in the form of red marks all over Hisoka's body, which reappear during encounters with Muraki, particularly in dreams. It is implied that they will disappear with Muraki's death, and only then will the curse be lifted. After Hisoka died, he became a shinigiami in order to discover the cause of his death since the doctor erased his memories of it.
Hisoka enjoys reading, and spends much of his time at the library by himself. His health even in the afterlife does not seem to be particularly well, and he has a tendency to faint. His lack of training and strength in comparison to Tsuzuki is also painfully apparent to him. However, he is a capable detective, and clever in subterfuge. It's also revealed that Hisoka has a fear of the dark due to being put in solitary confindement by his parents when he was still alive.
Although extremely reserved to the point of coldness, Hisoka deeply cares for other people. When Tsuzuki regains his suicidal tendencies, Hisoka comforts him and ends up preventing him from committing suicide once again. Hisoka also has a strong urge to take care of Tsuzuki, even though Tsuzuki drives him crazy sometimes it's hinted Hisoka has feelings for him. He maintains comfortable relationships with the rest of his co-workers, with the noticeable exception of Saya and Yuma, who constantly try to play with him like a doll.
Besides his empathy, Hisoka has also been trained in basic ofuda and defensive magic by Chief Konoe. Later in the series, he goes to seek out a Shikigami for himself in order to increase his power. Hisoka's first Shikigami is a Spanish-speaking potted cactus named Riko, a defensive and water-type Shiki. Hisoka is also adept in traditional martial arts, particularly archery, and kendo. His favorite color is blue, his favorite hobby is reading and his motto is "save money".