Train was orphaned at a young age when his parents were murdered. Left to survive on his own, he was eventually taken in and trained as an assassin by Zagine Axeloake, a cold-blooded hitman who instilled in him the belief that killing was a necessary part of life. Under Zagine’s influence, Train became numb to emotions and saw murder as a duty rather than a choice.

His deadly talents caught the attention of Chronos, a secretive organization that controlled the world’s balance through assassination and underground influence. Recognizing his potential, they recruited him into their elite assassination squad, the Chronos Numbers, where he became the 13th member, wielding his signature gun, “Hades.”

For years, Train served Chronos without question, efficiently eliminating anyone who threatened the organization. However, his encounter with Saya Minatsuki, a free-spirited sweeper, changed his perspective on life. Saya’s belief in freedom and choice made Train question his purpose, ultimately leading him to abandon Chronos and seek a new life as a bounty hunter.

His departure, however, earned him powerful enemies, including Creed Diskenth, a former admirer turned obsessive rival, who sought to bring Train back into a life of killing.

Train has messy dark brown hair and sharp golden eyes, giving him a feline-like appearance that matches his nickname, “Black Cat.” He is lean yet athletic, allowing him to move with cat-like agility in combat.

He wears a black sleeveless Chinese-style jacket with a high collar and gold trim, paired with black pants and boots. His most recognizable accessory is a choker with a small bell attached, a keepsake from Saya that symbolizes his newfound freedom.

His Chronos tattoo “XIII” is marked on the left side of his chest, signifying his former identity as Chronos Number XIII. However, after leaving Chronos, he begins embracing a more casual and relaxed appearance, reflecting his shift in personality.

Train Heartnet undergoes a significant transformation throughout Black Cat, shifting from a cold, detached assassin to a carefree and free-spirited bounty hunter. As a former Chronos Eraser, Train was emotionless, ruthless, and efficient, believing that killing was simply part of his duty. He followed orders without hesitation and maintained a distant, almost cynical outlook on life, never questioning his purpose or morality. However, his meeting with Saya Minatsuki sparked a change in his heart, as her philosophy of living freely and making one’s own choices made him realize that he was never truly in control of his own life.

After leaving Chronos and becoming a sweeper, Train adopts a much more easygoing, mischievous, and playful personality. He frequently jokes around, teases his teammates, and slacks off whenever possible, often frustrating his serious-minded partner, Sven Vollfied. Despite this, Train is deeply loyal to his friends and shows a strong sense of justice, choosing to fight for what he believes is right rather than blindly following orders. His transformation is not without struggle, as he still grapples with the weight of his past and the trauma of losing Saya, but ultimately, he emerges as a stronger and more self-assured individual, embracing his new life with optimism and determination.

Though he now tries to avoid killing, Train is not afraid to use force when necessary, particularly against dangerous enemies like Creed Diskenth. He firmly rejects his old assassin ways, but his battle instincts and sharp reflexes remain intact, making him a formidable opponent even without lethal intent. His carefree nature often masks his deep emotional scars, but he chooses to move forward rather than be defined by his past, proving that redemption and change are always possible.

• Leaving Chronos
  Train’s story begins with his defection from Chronos, an act that immediately makes him a target for both his former allies and new enemies. His decision to live freely rather than kill for an organization sets him on the path to becoming a sweeper.

• Battling Creed Diskenth
  Creed Diskenth, a former follower of Train during his Chronos days, develops a dangerous obsession with Train, believing that he is destined to become a god-like killer. After Saya’s death, Creed tries to manipulate Train back into his old ways, leading to a bitter conflict between them. Train, however, firmly rejects Creed’s ideology and vows to stop him from harming others.

• Forming New Bonds
  As a sweeper, Train partners with Sven Vollfied, a former detective, and Eve, a genetically engineered bio-weapon with nanomachine-enhanced abilities. Though they start off as reluctant allies, they eventually become a close-knit family, with Train acting as an older brother figure to Eve and frequently butting heads with Sven.

• Final Showdown Against Creed
  Train’s journey ultimately leads him to his final confrontation with Creed, where he fully embraces his new philosophy of life. Refusing to succumb to his past as an assassin, Train defeats Creed without killing him, proving that he has truly changed from the cold-blooded Black Cat of the past.