Tanaka serves as steward and former butler to the Phantomhive household. An elderly man with gray hair, a mustache, and a monocle, he is typically depicted in a diminutive form, dressed in a black suit and white gloves while holding a cup of tea. He can revert to his full height in critical situations.

His character embodies perceptiveness, dignity, and unwavering loyalty to the Phantomhive family. Having previously served Vincent Phantomhive, he survived the manor's 1885 attack, sustaining severe injuries while attempting to warn young Ciel Phantomhive to escape. As the massacre's sole surviving staff member, he received treatment at the Royal London Hospital.

Tanaka acts as a dependable adviser to Ciel, prioritizing the earl's well-being and sternly admonishing any perceived weakness in Ciel's role as head. Despite his age and reduced workload due to past injuries, he efficiently resumes butler duties when substituting for Sebastian Michaelis. He possesses exceptional combat skills, subduing assailants with Baritsu and demonstrating proficiency with a katana, including slicing bullets.

During the Atlantic voyage aboard the *Campania*, Tanaka accompanies the Phantomhive household to investigate the Aurora Society. He stands alongside fellow servants and Elizabeth Midford when Ciel presents her with an Easter egg, participating in the group's supportive presence. His involvement forms part of the collective household effort throughout the voyage.