Kayla "Kay" Kerry serves as the English dub name variation for Kei Yuki (有紀 蛍), a primary crew member aboard the spaceship Arcadia. She holds the dual role of chief navigator and science officer, steering the vessel and managing scientific operations during missions. Her physical appearance features blonde hair and brown eyes, typically clad in a pink suit bearing the crew's signature skull-and-crossbones motif.

Her background is marked by personal tragedy stemming from Earth government neglect; she lost both parents, her father dying after belittlement by a military officer. Kay retaliated by assaulting the officer, resulting in her imprisonment on a transport ship. Captain Harlock freed her during a raid, leading her to join the Arcadia's crew and share his commitment to challenging Earth's corrupt authority.

Initially hostile toward new crew members, particularly Tadashi Daiba (Terry Drake in English dubs) due to his early clumsiness and impulsiveness, she gradually forged a close platonic relationship with him, becoming one of his most trusted confidants. Later continuations like the SSX series contain subtle implications of unrequited romantic feelings toward Harlock, a dynamic unexplored in the original series.

Her skills extend beyond navigation and science; she demonstrates proficiency as a pilot, capable of operating the Arcadia itself and auxiliary spacecraft such as Space Wolf fighter jets during combat. Her resilience and combat aptitudes solidify her vital role within the crew's operational hierarchy.

Regarding nomenclature: "Kayla Kerry" originates not from official English dubs. Harmony Gold's adaptation renamed Kei Yuki as "Kay," while ZIV International's dub used "Carrie." "Kayla Kerry" emerged as a fan-constructed conflation of these variants, lacking basis in licensed media.