Eiko Tanaka is a founder of Studio 4°C, an animation studio that was established in 1986 along with Koji Morimoto and Yoshiharu Sato. The name "4°C" represents the temperature at which water becomes most dense, symbolizing high-quality work. Eiko Tanaka is also the CEO of Beyond C, a production company that initiated Tekkon Kinkreet, a project with Michael Arias. She served as an executive producer on both Tekkon Kinkreet and Mind Game, two Studio 4°C films. Additionally, she was an animation producer for Beyond and The Second Renaissance Part 1 in the Animatrix project. Prior to her work at Studio 4°C, Eiko Tanaka worked with Studio Ghibli as a line producer on My Neighbor Totoro and Kikis Delivery Service.