Hiyosu

Hiyosu cuts an unusual figure even among his fellow researchers, a bulky Shinigami whose green skin and swollen, misshapen head set him apart. A deep cleft runs from his forehead down to the nape of his neck, splitting his scalp into two halves and bearing the stitched marks of an old incision. Depressions like gills sit under his jaw on either side of his throat. His left eye is mechanically rigged so that turning a crank set into his temple pushes it out of its socket. In earlier years his complexion was ordinary and his head broader, with a defined line dividing it from his neck.

Possessive and self-satisfied, Hiyosu guards his discoveries jealously. When he uncovered Rukia Kuchiki's strange Gigai through his surveillance of the living world, he lingered over the footage and insisted the find belonged to him alone, brushing off Akon's ribbing. He lords authority over subordinates such as Rin Tsubokura, scolding him for slacking and packing him off to fetch tea, yet he is the first to gloat when his own work bears fruit.

Alongside his captain Mayuri Kurotsuchi and Akon, Hiyosu once took part in cruel experiments on captured Quincy, among them Soken Ishida, the grandfather and teacher of Uryu Ishida. In his role at the Institute he spotted Rukia hiding in the Human World inside an oddly built Gigai; once the artificial body was recovered, his examination confirmed that no one in Soul Society had made it. He and the other researchers went on to track the arrival of Yammy Llargo and Ulquiorra Cifer, flagging the newcomers as completed Arrancar, and later registered an Espada-level reading during a further incursion.

He is skilled enough with Kido to raise barriers and seal off sections of the Institute when it comes under threat. During the Thousand-Year Blood War, he attempts exactly that when Jidanbo Ikkanzaka storms the labs, only to be run through by Rin. He survives, and as the Wandenreich's shadows swallow the Seireitei he joins the remaining staff in trying to make sense of the impossible readings before Askin Nakk Le Vaar reveals that the enemy had been hidden inside the city all along. Ten years after Yhwach falls, he notes sensor readings almost identical to the emperor's own.