Miyu Matsuki was a Japanese voice actress and singer from Kure, Hiroshima, born on September 14, 1977. Her birth name was Mieko Matsuki. She was a graduate of Keio University's Faculty of Environment and Information Studies. Initially, her parents were not supportive of her career choice, but she pursued her goal after being accepted into university, which allowed her to move to Tokyo. She trained at the Nichinare narration school and the Aksent voice acting school, beginning her career under her real name in 1998 with a role in the PlayStation game Mikagura Shoujo Tanteidan. She later adopted the stage name Miyu Matsuki. In 2002, she secured her first major role in an anime television series, Seven of Seven. That same year, she joined the talent agency 81 Produce, with which she was affiliated for the rest of her career.

Matsuki built an extensive and diverse filmography across anime, video games, and film. She was well-known for a wide array of characters, demonstrating her range and versatility. Some of her most notable and recurring roles included Magical Sapphire in the Fate/kaleid liner Prisma Illya series, Choppy in the Futari wa Pretty Cure Splash Star franchise, Kuuko in the Haiyore! Nyaruko-san series, and the eccentric Yoshinoya-sensei in Hidamari Sketch. She also voiced Isumi Saginomiya in Hayate the Combat Butler, Anna Nishikinomiya in Shimoneta, Flora in Claymore, and Hisui in the Carnival Phantasm series, among many others. Her work also extended significantly into video games, where she lent her voice to characters such as Lailah in Tales of Zestiria, Claire Rieveldt in The Legend of Heroes: Trails of Cold Steel, Chihaya Mifune in Persona 5, and Hisui in the Melty Blood fighting game series. The sheer volume of her work, including many of the specific roles listed in the query, such as those in the Dog Days, Tamayura, and Sayonara Zetsubou Sensei franchises, is well-documented across her filmography.

In 2013, Matsuki was a recipient of the Best Musical Performance award at the 7th Seiyu Awards, alongside Kana Asumi and Yuka Ōtsubo, for their work on the opening theme song for Haiyore! Nyaruko-san. In July 2015, she announced that she was taking a temporary leave from her career to undergo treatment for acute pneumonia. On October 27, 2015, she passed away in Tokyo at the age of 38 due to lymphoma resulting from a chronic active Epstein-Barr virus infection. Her ongoing and scheduled roles were subsequently taken over by other voice actresses, including Yui Horie, Yumi Kakazu, Reina Ueda, and Noriko Shitaya. In September 2016, a charity event titled "39! Miyu-chan" was organized in her honor by her friends and colleagues, with proceeds going towards research for chronic active Epstein-Barr virus.