Hiyosu

is a department head in the Research Institute tied to the 12th division.

Character Outline
He is a large man with a bulbous head and an extendable eyeball via a crank on his head. He was the one that originally discovered Rukia Kuchiki's unusual gigai. He was also present when the Research Institute discovered that Yammy and Ulquiorra had begun a small invasion on Karakura Town.

Trivia
He is one of the few Shinigami within the Gotei 13 who doesn't take on the appearance of a Human.