Shizuka Namino is a Mazone, a humanoid plant species from beyond Andromeda. She infiltrates Earth as the Prime Minister's Secretary, conducting espionage and sabotage against human forces, specifically targeting the spaceship Arcadia and its crew.

She orchestrates an assassination attempt on the Prime Minister, framing Earth commander Kiruta for the crime. After facilitating Kiruta's escape, she manipulates him into securing her refuge aboard the Arcadia by falsely claiming treason against her own people. Her mission on the Arcadia focuses on identifying the vessel's mysterious forty-second crew member and sabotaging it from within.

Her cover is eventually blown, revealed to Captain Harlock. Following her exposure, the Mazone Queen Lafresia disavows and abandons her. Despite her espionage, Harlock grants her freedom and intervenes to save her when Mazone forces attempt to eliminate her.

Torn between Mazone loyalty and a growing respect for Harlock's honor, she engineers a confrontation where Harlock is forced to kill her, resolving her guilt over the failed mission and her admiration for her adversary. After her death, Harlock conceals her true Mazone identity from Kiruta, who cared for her, instead stating she died heroically fighting the Mazone fleet.

In the OVA *Endless Odyssey*, a holographic assistant to Dr. Daiba resembles Shizuka Namino, sharing her physical appearance, dress, and pendant, but possessing dark hair consistent with the manga depiction. This hologram is explicitly a separate entity and not the original Shizuka Namino.