Hiyori Sarugaki is a former lieutenant of the 12th Division in the Gotei 13, having served under Captains Kirio Hikifune and later Kisuke Urahara. She is currently a member of the Vizard, a group of Soul Reapers who acquired Hollow powers following a betrayal by Sōsuke Aizen over a century ago. Physically, she has the appearance of a young girl with a small, thin build. Her blonde hair is typically worn in two short pigtails, and she has brown eyes, freckles on her cheeks, and a notably elongated left upper fang. Her standard attire is a red tracksuit decorated with the first kanji of her name, and she is often seen wearing a baseball cap. In her past life in Soul Society, she wore the standard Soul Reaper uniform with a lieutenant's armband and kept her pigtails longer.

Hiyori's personality is defined by aggression, a notoriously short temper, and violent tendencies. Despite her small size, she is confrontational and impulsive, often resorting to physical abuse, typically by kicking or striking others with her sandal. Her most frequent target is Shinji Hirako, whom she has berated and attacked since their time together in Soul Society, despite his former rank as a captain. This behavior extends to most people around her, including Kisuke Urahara, whom she initially refused to accept as her new captain, and Ichigo Kurosaki, whom she trained. She shows very little patience and has a habit of yelling at others. However, her harsh exterior masks a more emotionally sensitive interior; she is deeply affected by the departure of those she respects and has admitted to harboring a deep hatred for both Soul Reapers and humans, stemming from her inability to belong to either group after becoming a Vizard. The creator has described her with the keyword "fierce."

Hiyori was highly devoted to her first captain, Kirio Hikifune, whom she viewed as a mother figure. When Hikifune was promoted to the Royal Guard, Hiyori was deeply hurt and resentful, taking out her anger on her new captain, Kisuke Urahara. Over time, she eventually adapted to his leadership and became the third seat of the newly formed Research and Development Institute under him, though she frequently clashed with her superior, Mayuri Kurotsuchi. Hiyori and Shinji Hirako share a deeply ingrained, belligerent relationship characterized by constant fighting and insults, yet there is an underlying layer of mutual understanding and care. She is often seen as the instigator of chaos within the Vizard group, but despite her abrasive personality, she is considered a valued member of this unconventional family. Her role in the story becomes prominent when the Vizard take an interest in Ichigo Kurosaki. She is tasked with being the primary physical trainer for Ichigo, forcing him to gain control over his inner Hollow through brutal combat, a process she herself had undergone with one of the longest struggle times in the group. She also serves as an initial antagonist to Ichigo's friends, displaying her distrust of humans by threatening Orihime Inoue and Yasutora Sado.

As a Vizard, Hiyori possesses the combined powers of a Soul Reaper and a Hollow. Her zanpakutō is named Kubikiri Orochi. Its released state, achieved with the command "cut them down," transforms the blade into a large, notched cleaver-like weapon, though its specific special abilities are not extensively detailed. Her Hollow mask is distinct, featuring a single long horn extending from the forehead area and a pattern of diamond-shaped markings. By donning the mask, she gains a significant boost in power, speed, and durability, as well as access to Hollow abilities like the Cero. Beyond her spiritual powers, she is very proficient in hand-to-hand combat as a primary fighting method.