Hyōgo Sakai, originating from Sumiyoshi in Settsu Province, served as an accountant (kaikei-gata) for the Shinsengumi during Japan's late Edo period. His exact birth year is undocumented. He participated in events like the Ikedaya Incident, earning a commendation of 15 ryō. Historical records list him alongside notable members such as Harada Sanosuke and Yamanami Keisuke. Around 1865, during the Keio era, he fled the Shinsengumi under unclear circumstances. Theories about his escape suggest he was overwhelmed by fear during burial duties or that he was later assassinated by Shinsengumi members, potentially including Okita Sōji. A tombstone in Itabashi memorializes him, indicating his death occurred shortly after his departure.

In anime adaptations, Hyōgo Sakai appears as a tall young man with long black hair, typically tied in a ponytail. He is frequently depicted wearing a simple blue kimono and maintains a smiling demeanor. His personality is characterized by amiability and compliance; he actively strives to maintain harmonious relationships within the group and expresses pride in wearing the Shinsengumi's distinctive blue haori. As an only child, he supports his parents financially by sending portions of his earnings from Kyoto. Despite his accounting role, he demonstrates proficiency with the sword and exhibits a willingness to risk his life to protect his comrades.

The character appears in the 2021 OVA series, consisting of three parts released between December 2021 and February 2022.