Marco Owen is the male main character of the series.
Marco is a very handsome dark olive-skinned young man with chin-length jet black hair and hazel eyes. He also has many intimidating tattoos all over his body, which become his trademark. He is also shown to be very tall, muscular and well built.
Marco wears an black leather jacket, pattern shirt inside, dark green pants and combat boots. But he appears to be shirtless overall unlike many male characters in the series.
Marco is a fearsome, barbaric, intelligent, laid back and easygoing man who is a expect hacker and former CIA agent that is skilled at espionage and also with weapons. Despite his criminal history, he worries a lot about the other survivors, regardless of the fact that none of them have more than six weeks to live. He has regularly put his mind on the line to save the others, especially even those who resented him. It also arguable that although he has certainly not been upfront with information, he has never actually flat-out lied to any of the survivors. Marco is also the unofficial leader of the group, due to his knowledge and natural capabilities.
He is an expert hacker, so much so that he was able to crack through the CIA's computers – and those of Venus Gate, something that had him arrested and incarcerated for more than half a century (during the events of the manga, he still had 60 years to serve in prison). While a prisoner he was approached by the NSA, which offered him complete parole for his crimes in exchange of his help in dealing with the Medusa affair.
Very little about Marco Owen other than the fact, he was a criminal who had gotten into trouble with the CIA by hacking their database for unknown reason. He has many layers to him and seem to know a good deal more than any does. While in prison, Marco built up his muscles, received tattoos and acquired a new attitude that makes him comes off as a thug more than of a CIA agent- so much so that his intelligence with anything surprises Katherine and Peter, despite already knowing who he was.
The Medusa virus incident
Becoming a de facto spy for the Great Britain, he was sent as a patient to the gathering at Venus Gate labs, the same where all the other main characters were sent, in order to assert the objectives of the gathering, gather evidence on the mysterious Level 4 labs of the island, and also to pursue a personal vendetta against his old friend Zeus, who framed him for crimes he did not commit before vanishing. He was trying to accomplish what he was sent to do when the Medusa outbreak and Shizuku Ishiki's awakening occurred and in the ensuing chaos he was left unconscious. Thus, he was able to present himself to the other survivors as one of them.
Marco acts tough, and his overall appearance and mannerisms leave the other survivors highly suspicious of him, especially when they discover that he never had the Medusa virus in the first place. Nevertheless, given the fact that he is the most skilled of them all, Marco is silently accepted as the leader of the group, at least until he goes on his own to try to find Zeus. He was also the first of them to encounter the ghostly apparition of Alice, and on more than one instance was seen arguing with her. Also, he himself was suspicious of Kasumi Ishiki after seeing video footage of her twin sister Shizuku trailing after the wave of monstrous beings that erupted from Level 4.
During the climax of it, he died once, killed by Zeus's artificially created beast soldiers, though his corpse was later found and resurrected by Alice, a deed for which she sacrificed her life. He was thus able to face Zeus head-on by literally hacking into him and, finally, completely erasing him for good. What happened to him and Kasumi after they saved themselves is left to the reader to speculate, though apparently their feelings for each other were mutual.