Luna appears across multiple Casshern franchise iterations with distinct backgrounds and roles.

In the original 1973 *Neo-Human Casshern* series and the 1993 OVA *Casshan: Robot Hunter*, Luna Kozuki operates as a 15-year-old human resistance fighter. She allies with Casshern against Braiking Boss's robot army. Her scientist father's legacy includes an electromagnetic field gun she wields against robots. She executes missions like delivering weapon plans to human forces and survives capture through Casshern's intervention.

In *Casshern Sins*, Luna becomes "the sun that was named moon," a pivotal figure embodying life and salvation. Created to grant death as release from eternal suffering, she resides in a sanctuary guarded by devoted robots including Dune, Lyuze, and Liza. Braiking Boss orders her assassination by Casshern, triggering the Ruin—a global cataclysm causing universal decay. Luna later resurfaces altered after Casshern's blood mixes with hers during death. This transforms her philosophy: she now despises death and selectively grants eternal life exclusively to decay-free beings, denying salvation to entities like Dune. She seeks a deathless world by allowing Ruin-afflicted beings to perish.

Her abilities shift between incarnations. In *Casshern Sins*, she initially wields "Blood Salvation" through her blood to end eternal life. Post-resurrection, her blood grants immortality and reverses decay solely to chosen recipients. She also removes desired traits, such as stripping Leda's beauty. Though inherently immortal, she remains susceptible to termination as proven by Casshern.

Luna has no documented presence in the 2004 live-action film *Casshern*.