Serge Train, a 20-year-old haunted by amnesia, joins the counter-virus organization STAND seeking answers about his origins. His crimson combat Gear, Halcyon Scarlet, is pre-programmed to his unique physical and mental specifications, hinting at STAND’s leader Raven’s foreknowledge of his existence. Recurring nightmares and an unexplained bond with a phenomenon called the Incubator drive Serge to attempt assassinating Raven during a mission. Despite this betrayal, Raven recruits him for his unparalleled combat prowess, which eclipses even seasoned STAND operatives.

Serge’s fragmented memories and dormant abilities stem from his identity as a clone of Dr. Milan Trane, a scientist aboard the Helio-Lab IV satellite during the catastrophic "Black Valentine" incident. The project’s attempt at extraterrestrial communication birthed the Virus after contact with an unknown entity. Raven, the incident’s sole survivor, cloned Trane to create Serge, intending to exploit his genetic ties to the Virus for clandestine ends.

Within STAND, Serge clashes with Jouichirou, a veteran resentful of his rapid ascent, while forging a bond with Erika Tinen, a teammate from a similarly destitute past. Their relationship deepens, culminating in Erika’s pregnancy—a revelation she prepares to share as their journey nears its conclusion. Interactions with Raven and Donna, a cryptic holographic entity, slowly unveil Serge’s cloned origins and his role in Raven’s schemes, though obscured truths linger.

In combat, Serge relies on raw instinct and adaptability, defying conventional training. His psyche grapples with fractured identity and haunting visions, mirroring themes of synthetic creation and inherited fate. The clash between his thirst for vengeance against Raven and his quest for self-discovery anchors his tumultuous narrative, leaving his ultimate path unresolved.