Hikaru Isshiki is a Japanese voice actress born on July 28, 1973, in Tokyo. She is a freelance voice actress who was formerly affiliated with agencies such as Arts Vision and Pro-Fit. Isshiki Hikaru is an alias used primarily for her extensive work in adult animation and games, while she also performs under her legal name, Ryoko Tanaka, for mainstream projects.

Her career began in 1997, and she quickly became a prominent and respected figure in the adult video game and animation industry, often referred to as a "heavenly king" in the field of eroge. She is recognized for her experience and skill, frequently voicing characters with a cool, calm, and collected demeanor known as kuudere, as well as trustworthy and cheerful older sister types. This typecasting aligns with her personal admission that she finds it more challenging to play very young characters, as the older sister or composed roles suit her natural voice and personality better.

As Hikaru Isshiki, her filmography includes a vast number of roles that correspond directly with the titles mentioned by the user. She is credited as Kozue Takama in Lover-in-Law, Saori Shirakawa in Four for Fourplay, and Akina Miyazawa in Issyo ni H Shiyō. Other notable roles under this alias include Ryōko Shirakawa in Anejiru The Animation, Nana Takashiro in Cartagra - Tsukigurui no Yamai, and Keiko Nagumo in My Classmate's Mother. Her credits also encompass Arisa Minase in Trick or Alice, Ayane Tachibana in Perverted Thomas, Natsume Takashiro in Girl in the Shell, and Epanatica in Evil Woman Executive. She also played Fumi in MILF Mansion.

Under her real name, Ryoko Tanaka, she has achieved recognition for her roles in mainstream anime and video game franchises. She is well-known for voicing Yuiko Kurugaya in the Little Busters! series and its crossover Kaginado, Yumiko Sakaki in The Fruit of Grisaia series, and Touka Nishikujou in Rewrite. Her other mainstream credits include Kasumi Suda in _summer, Hikari Kuroda in School Days, Tsubomi in Shuffle!, and Kyōko Hōin in Kodomo no Jikan. She also had a role as Tsuyu Kamata in Tokyo ESP. In video games, her work as Tomoyo Sakagami in Tomoyo After: It's a Wonderful Life is particularly notable.