We eventually learn why: Einstürzende noticed Heine's exceptional abilities and wanted to experiment on him and attach the "Master" spine to his body. Heine accepts under the hope that with it, he'll be stronger and better able to help his friends escape. Unfortunately, once the spine begins to successfully fuse to his body, Einstürzende decides that she doesn't need the other test subjects anymore and has them kill each other. Heine escapes the "Master" process early but not enough to stop himself from disemboweling Lily while under control of the Spine.
Heroic RROD: Yes, you read that correctly. In chapter 72, thanks to Naoto, whom Einstürzende briefly takes control of, Heine ends up with a stab wound straight through his gut since Naoto's sword is specially made with a poison for dealing with Cerberus spines.
My Greatest Failure: Heine inadverdently caused the deaths of all his friends/family before escaping the organization. He truly regrets accepting Einstürzende offer.
He even tries to cheer Naoto up after her second Heroic BSOD.
YMMV but his seemingly trying not to hurt Naoto while she's possessed by Einstürzende and even resisting the influence from his spine when it wants to kill her.
Scars Are Forever: Badou has scars on both his right hand and right eye (underneath the eyepatch). These are implied to have something to do with his older brother, but little more than a very brief, bloody flashback has been shown so far to explain the wounds.
Cloning Blues: The other Naoto calls her "Double" or "Spare."
It's even worse. She's actually a perfected clone of Campenella Fruhling, the original Naoto and made specifically for Einstürzende to transfer her consciousness into.
Grand Theft Me: Ultimately what Einstürzende plans for Naoto. Naoto is taken from the organization before she can attempt it the first time and is rescued by Badou during the second attempt.
Heroic BSOD: When she glimpses a pair of eyes she recognizes from her past.
Naoto seems to be having a lot of these as of late. They're affecting her mind more than her body.
You Killed My Parents: The reason she trained with Fuyumine was to one day kill him. Subverted when he is killed by someone else and it turns out he was innocent anyway. She is now looking for their true killer.
My Greatest Failure: Is very bothered by the fact that he was unable to stop his student from murdering the woman he loved. He's even MORE bothered by the fact that his student even turned out that way.
A Mad Scientist working for an as of yet unnamed underground organization.Giovanni and Heine occasionally call her "Mother."
Abusive Parents: To the Cerebus spine children, many of whom are possibly her actual children. She makes them fight huge monstrosities to earn her fleeting love.
Ax Crazy: She has yet to pick up an actual weapon but someone who smiles while people are getting mauled barehanded is not right in the head.
Back from the Dead: The original body is killed (or at least one of them is) by Heine. Another body walks up and keep talking to Heine and Magato as if nothing happened.
Body Surf: She's a Cerebus spine person too but instead of healing, she can just transfer her consciousness into another body. After Heine shoots the first one to death, her next body is Lily.
Hive Mind: There are at least three other Einstürzende working in her organization. All of them look relatively similar and are modified to share experiences and memories when one dies.
Yandere: Showers those who do well against her creations with affection, is rather callous to those who don't but still have the nerve to survive.
Campenella Fruhling
A hired gun swordswoman who appears to be working with Einstürzende. She leads a troupe of helmeted, black-clad Nigh Invulnerable minions. Nuki and Loki's apparent guardian. Recently revealed to be the original Naoto & also the killer of Naoto Fuyumine's parents.
Affably Evil: Rather polite and formal to Bishop, even leaving him her name.
Badass Boast:"Forgive the lack of ceremony but I have to kill anyone who sees us. Any last prayers?"Bishop escapes and is blind, so technically this is still true.
Badass Normal: Assuming she doesn't somehow have a Cerebus spine.
Two young twin girls who are always together and work as bounty hunters. They are under Fruhling's care and apparently part of Einstürzende's organization.
Vague Age: Or perhaps, Younger Than They Look. In the prequel, Magato seems noticebly older than Naoto (early 20's vs mid teens) whereas in the series proper, he seems 5 years older at the most.
The reason for this is Magato, while still very much younger, is from Fruhling's generation at the organization.
Wild Card: No one is sure who's side Magato is on. He seems a bit obsessed with killing Naoto but expresses something resembling fraternal concern when her fighting style becomes inexplicably more cutthroat. He also drops his fight with Heine over the suspicion that she's in danger. It's implied that the only thing Magato cares about in any intense manner is Naoto but for what reason, purpose or even if this is a good thing hasn't been explained yet.
Relative Button: He invokes this with Naoto after he killed her parents. As it turns out, he didn't; he just told her that so that it would give her the strength to keep living, if only to live long enough to kill him first.
Silent Scapegoat: To Naoto, because it gave her a reason to live.
The Reveal: He's both a former colleague of Einstürzende and another person with a Cerberus spine, specifically the original, the Führer, and is waaay stronger than Giovanni. He's also in league with Ernest.
Shout Out: To Einstürzende Neubauten, like Angelika.
Arch-Enemy: He's behind what happened to Dave Nails, making him one to Badou.
Ax Crazy: Smiles while sending a horde of mind-controlled musicians after Badou and Mihai.
Evil Genius: Times the explosions he's set around the city to go off in time with Giovanni's Black Soldiers and can apparently hypnotize random people he meets in the street to be his mindless slaves.
Faux Affably Evil: Introduces himself as a gentleman. He then makes his entire orchestra attack Badou before revealing himself as the reason Dave is missing.
Knife Nut: He's also responsible for Badou's scars and eye.
Mind Control: Of an entire orchestra and somehow he makes Mihai shoot Badou. It hasn't been revealed how he's doing this.
