Teiko, also known as Nanahara Teiko, is a Japanese voice actress and singer from Tokyo, born on October 14, 1996. Her career in entertainment began in the music industry, where she performed as a vocalist for the indie band Elise Shōjoshiki and was also a member of idol units such as Sugar Qualia and Jikou Kokka. This musical background directly led to her entry into voice acting.

In 2016, Teiko performed as a guest singer at a live concert attended by acclaimed anime director Kunihiko Ikuhara. Impressed by her performance, Ikuhara later cast her in his original anime television series, Sarazanmai. This role, as the local Asakusa idol Sara Azuma in 2019, marked Teiko's debut as a voice actress. Her involvement with the character extended beyond voice work; she performed the insert song "Hōkago Kappa" for the anime as Sara Azuma with her band, Elise Shōjoshiki. She later reprised this role for the 2019 stage play adaptation, Sara ni Sarazanmai ~Ai to Yokubō no Stage~.

Following her debut, Teiko continued to build her career in both anime and video games. Her anime roles have included Sakura in Uchitama?! Have you seen my Tama?, a female student in Horimiya: The Missing Pieces, and Yukiyama Usuyama in the 2025 series Medalist. In the video game industry, she has lent her voice to characters in titles such as Soul Ark, Memorial Record, Monsters Strike, Alice Fiction, and Sakura Revolution.

Throughout her career, Teiko has been affiliated with different talent agencies. She initially joined Stardust Promotion in 2019 before moving to her current agency, Crocodile, in 2022. It was also in 2022 that she transitioned to using the stage name Nanahara Teiko, having previously performed under the names Teiko and Kagohara Teiko.