Keiko Kobayashi is a Japanese voice actress from Niigata Prefecture, born on September 3rd. She began her career in 2006 after graduating from the voice actor department of the Amusement Media Academy. Initially affiliated with the agency Power Rise through its predecessor Toritori Office, she became a freelance voice actress in May 2023. She is known for her versatile vocal talent, bringing to life a wide range of characters from main heroines to quirky side characters, mystical creatures, and spirits.

One of her notable anime roles is Lady Momona in the 2014 television series Lady Jewelpet. She has a significant recurring presence in the Precure franchise, voicing multiple characters in Maho Girls Precure! in 2016 and its subsequent installments, as well as appearing in Go! Princess Precure. Her other anime credits include Bakumatsu Rock and OVA projects like Terminal Harem VR.

Beyond anime, Kobayashi has an extensive portfolio in video games. Her game roles include Cai Yulian in Fate/Samurai Remnant, Bianca in STELLA GLOW, and Kurumi Miyagishi in the PhaseD series. She also contributed to titles such as Ragnarok Online, PriministAr, and the mobile game Guardian Project. Her work extends to drama CDs, including the Fate/Zero Sound Drama series, and she has performed in movie dubbing and television narrations, such as for a Meiji commercial campaign.

Kobayashi has also been active in live performance. She was a member of the anime song unit Heavy Snow, performing in live events with fellow voice actors. She has participated in numerous stage readings and fan gatherings. For roles in adult-oriented anime and video games, she uses the aliases Mizuki and Sena Yuzuki. While she has not received major public awards, her consistent and heartfelt performances, particularly in magical girl and fantasy genres, have earned her recognition and a dedicated fan following.