The Demi-Hollow

The first appeared as a  that was chained to an abandoned Karakura Town hospital. He is turned into a Hollow thanks to the interference of Don Kanonji and later purified by Ichigo.

Appearance
While still in his Jibakurai form, the Demi-Hollow looked like a man in his early to middle thirties with short spiky dark hair and sideburns, wearing a long sleeved T-shirt. After his transformation he turns into a medium sized bipedal Hollow with a mask resembling the face of a frog and two long extensions coming out the sides of its mask, resembling pigtails.

History
Before his death, the Demi-Hollow was the older son and heir of a rich hospital owner. He had planned to live the good life once he inherited the hospital and started raking in money from its profits. When his father died he left the hospital to his younger brother instead, which caused his spirit to be bound to the hospital after death.

Trivia

 * The Demi-Hollow is dubbed as such in the SOULs databook, even though he becomes a full Hollow shortly after his debut and retains this form for the remainder of his story.
 * The two extensions on his mask were omitted in the anime.