Eiko Tanaka founded Studio 4°C back in 1986 alongside Koji Morimoto and Yoshiharu Sato. The studio's name—4°C, the temperature at which water reaches maximum density—was chosen as a kind of mission statement about pursuing quality. She's still the president there.

Beyond that, Tanaka runs Beyond C, a production company she heads as CEO. That's the outfit that partnered with Michael Arias on what became Tekkon Kinkreet, one of her key projects as executive producer. She brought the same role to Mind Game, another major Studio 4°C film, and worked as an animation producer on The Second Renaissance Part 1 for the Animatrix anthology.

Before starting 4°C, Tanaka was embedded at Studio Ghibli as a line producer on My Neighbor Totoro and Kiki's Delivery Service—early credits that shaped how she'd approach production later on.