Tomoko Kotani is a Japanese female voice actress affiliated with the talent agency 81 Produce. She was born on September 29, 1968, in Kanagawa Prefecture, Japan. Kotani began her career in the late 1990s, taking on minor roles in television series. Her early credits include a small part as a female student in the 1997 anime Nightwalker and as a librarian in the 1998 series His and Her Circumstances. She also voiced the character Setsuka Nogami in the 1998 series Professor Pain.

Kotani's career became more prominent in the early 2000s. In 2000, she was cast in a leading role as the skilled and acrobatic gun expert Mikura Suzuki in the original video animation Mezzo Forte. This action-oriented role showcased her ability to voice strong, central characters and she would reprise the character of Mikura Suzuki in the 2004 television series adaptation, Mezzo DSA. Another significant role from this period was as Sumie Nishino, the mother of one of the main characters, in the 2004 television series This Ugly Yet Beautiful World.

Throughout the 2000s, Kotani continued to build her filmography with a variety of supporting roles. In 2002, she voiced the character Tsukie Kayano in the television series Seven of Seven. Her work in 2004 included voicing Junko Asagiri in the series Desert Punk and Yuki in the series Kujibiki Unbalance. She also took on the role of Mikura Suzuki in Mezzo DSA that same year. Later in the decade, she voiced a character named Shigeko in the 2009 television series Aoi Bungaku Series.

Kotani's performance as the character Mikura Suzuki in Mezzo DSA has been noted as a standout in her career. The series featured a cast of relatively unknown voice actors at the time, and her portrayal of the lively, quick-witted, and fearless Mikura was highlighted as particularly impressive and memorable.