Kotoko Sasaki is a Japanese voice actress and former idol singer born on August 28, 1998, in Saitama Prefecture. She began her entertainment career as a second-generation member of the popular idol group Nogizaka46, a role she held from 2013 until her graduation from the group in March 2020. Following her departure from the group, Sasaki transitioned into voice acting, joining the agency Style Cube in October 2020 to pursue this new path.

Her early voice acting work included a series of minor roles in anime series. She voiced a town girl in the 2022 series Tensei shitara Ken Deshita, and performed roles as a schoolgirl in several other productions, including Nanatsu no Maken ga Shihai Suru in 2023 and Koi wa Futago de Warikirenai in 2024. She also provided narration for television programs and voiced characters for video games such as Kemono Friends 3 and Code Geass: Lost Stories.

Sasaki was selected for her most prominent and recognized role to date in February 2023, becoming the voice of Tsuzuri Yūgiri, a second-year student at Hasu no Sora Jogakuin, for the Love Live! franchise. This role is featured across multiple media, including the smartphone app Link! Like! Love Live! and the film Love Live! Hasu no Sora Jogakuin School Idol Club: Bloom Garden Party.

Prior to her voice acting career, Sasaki had a notable tenure in Nogizaka46, where she was known for her appreciation of anime, a passion she developed due to her brother's influence. One of her achievements includes hosting a radio corner titled Nogizaka46 no Sasaki Kotoko no Top Gear, which was nominated for awards at the sixth Anime Radio Awards. Since transitioning to voice acting, she has also taken on the role of a regular narrator for the science program Galileo X and has served as a public relations ambassador for her hometown of Honjo in Saitama Prefecture.