Michiko Hirai was a Japanese actress and voice actress born in Tokyo on September 9, 1935. Her career in entertainment began at a young age; from around ten years old, she was active as an exclusive singer for NHK. She later graduated from the music department of Ferris Women's Junior College. In 1957, invited by Kazuo Kumakura, she joined the theatre company Theater Echo, where she would remain for the duration of her career.

While she was a leading actress in her theatre company, Hirai also built a prolific career as a voice actress, becoming a familiar presence in the early days of Japanese television animation. Her most iconic and foundational role was originating the character of Sally Yumeno, the titular character in the 1966 anime Mahōtsukai Sally (Sally the Witch). This role made her a household name and established her as a pioneer in the magical girl genre. Other significant anime roles from this era include Ran in Ryu, the Cave Boy, Miki Kōda in Nozomi in the Sun, Fifi in Panda no Daibōken, and Anna Robinson in Swiss Family Robinson. Her voice was also widely recognized as Starsha, the queen of the planet Iscandar, in the influential Space Battleship Yamato series.

Beyond anime, Hirai was highly active in voice dubbing for foreign films and television series. She was particularly well-known as the regular Japanese dubbing voice for American actress Faye Dunaway, featuring in many of her films for television broadcast. She also provided the Japanese voice for actresses such as Catherine Deneuve. Her work in dubbing extended to Western animation as well; she voiced Cruella de Vil in a 1981 dub of One Hundred and One Dalmatians and Lucy Van Pelt in Peanuts specials.

Hirai balanced her voice work with a continued career on stage. Her talent as a stage actress was formally recognized when she won the 18th Kinokuniya Theater Award for her performance in the play The Gingerbread Lady in 1983. She was married to fellow voice actor Shinji Nakae.

Michiko Hirai passed away on July 3, 1984, at the age of 48 due to acute heart failure. Her final performances were broadcast posthumously: her voice role as Mrs. Dracula in Lupin the Third Part III aired four days after her death, and her live-action role in the drama Onna goroshi abura no jigoku was broadcast two months later. Following her passing, several of her prominent roles were succeeded by other voice actors, including her role as Starsha in the Space Battleship Yamato franchise, which was taken over by Yumi Nakatani and later Miyuki Ueda.