In the Manga  The mysterious "Doctor" is a highly talented scientist who is interested in nanomachines. His desire to know reaches the level of psychosis, and he cares little for any lives he may take or destroy in his pursuit. He reattaches Train's right arm after it is severed by Creed's Imagine Blade, at Creed's request, and later captures Eve, intending to dissect her. The Doc's Tao Power is called "Warp World," and it allows him to literally create an alternate world where everything he imagines becomes reality. He can also pull memories from the minds of those trapped in the Warp World, and bring those into reality as well. He has no relation with Dr. Tearju or the creation of Eve or Eden in the manga.  In the Anime  The Doctor appears to be the same as in the manga. He never reattached Train's arm (since that scene never happened in the anime) nor did he capture or attempt to dissect Eve. However, he plays a major role in the Eden project, as he is the one who controls Adam's actions towards uniting Eve with Eden, by simply playing cue-ball. After talking to Dr. Tearju through his computer screen, where it is revealed he was the one who retrieved Eden's data that Dr. Tearju tried to destroy, he participates in the battle between the heroes and the Zero Numbers, where he transforms himself into a monster (although only his transformation is seen in one scene, circumstantially, and is never seen in full-body). He looks quite similar to Kilnorton from The Law of Ueki minus the ponytail.  Source: Wikipedia

Train Heartnet is the infamous gunman 'Black Cat', a cold-blooded assassin who works for the organization known as 'Chronos', bearing the mark XIII on his body. Most of his life was surrounded by violence, so Train is quiet, asocial and uncaring. However his life changes as he encounters the mysterious Sweeper (bounty hunter), Saya. Her unique way of living interested Train but tragedy occurs, resulting in Train changing the way he has lived towards the life of a Sweeper with newfound friends Sven and Eve.

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Married to fellow voice actor [Brandon McInnis](https://anilist.co/staff/127809/).

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Train Heartnet, also known as "Black Cat," was an infamous assassin for a secret organization called Chronos...until he abandoned that cold-blooded existence to live on his own terms as an easygoing bounty hunter. But is Train's past as far behind him as he thinks?
 
(Source: Viz Media)

DVD only episode 15. Creed seeks out media attention to reveal the existence of Chronos. Meanwhile, Sephiria seeks out Train to untangle the riddle of his desertion, but becomes the unwitting prey of a defector of a far darker nature. (Source: Crunchyroll)

Kousuke Kanzaki