"Contractors are liars. I'm no different."
A note: I try to use Li when Hei is totally using his alias persona and Hei when he drops it (such as fight scenes, etc).
There isn't much known about Hei before he joined up with the Syndicate, other than he enjoyed watching the stars. He also seen looking after his sister Pai. Then, ten years ago, the real stars in the sky vanished. They were replaced with fake stars, each one tied to a human who had become a Contractor, someone with special powers. Passive mediums known as Dolls also make an appearance around this time. Pai becomes a Contractor, BK-201, and Hei joins her in the Syndicate, intent on sticking close no matter what it takes. She might not act human anymore, but Hei is willing to learn the trade of an assassin and get caught up in Syndicate business just to watch over her. In flashbacks, it's seen that Hei doesn't particularly enjoy all the killing he does, but he's a highly effective assassin which earns him the nickname 'The Black Reaper'.
During Heaven's War in which several countries fought over the sudden appearance of Heaven's Gate in South America, Hei and his team are sent into the fray. Shortly after, everything and everyone within a 1500 kilometer radius of Heaven's Gate vanished. Nothing can reach inside this zone and comes ever comes out. Pai vanishes, as does the rest of Hei's team, and Hei emerges from the event as a Contractor and the 'new' BK-201. He remains with the Syndicate, but continues to try and find clues to his sister's whereabouts.
The show picks up five years after the events at Heaven's Gate, in Toyko. Hei has a new team; Huang, the go-between and sort of group leader, Mao, a fellow Contractor, and Yin, a Doll. The police are attempting to arrest Louis, who is a Contractor working for the French government, but he escapes using his anti-gravity nullification ability and lands on another rooftop. After breaking his own fingers as payment for using his Contractor power, Louis is confronted by Hei, whom Louis tosses into the air using his power. Hei, however, uses his steel wire to ground himself to the railing and then again to choke Louis. He interrogates the other Contractor, driving the hilt of his knife into the man's broken fingers, kicking and hitting him. Louis only says a woman has whatever Hei is looking for. Hei is disgusted with the man and clamps his hand down on his head. Mao protests killing the Contractor, but the next scene shows Louis dead as the police search the rooftop for clues.
The next day finds Hei posing as a Chinese transfer student; Li Shengshun. It's quickly apparent how different Hei and Li are from one another. When Li shows up to a small apartment building where he is promptly yanked inside the landlady's flat, thinking he's a TV repairman. Li goes along with this, however, and hits the TV a few times, it sparks and the reception returns. The landlady takes him up to his new apartment where Li runs into another new tenant; a woman going by the name Haraguchi. She doesn't say anything to Li and leaves the building , presumably on her way to work. The Contractor enters the stark apartment and searches it (probably for bugs or taps). He's been sent there to run into Haraguchi and procure the items the Syndicate wants.
Later that evening, however, the police are searching for Chiaki Shinoda in a bar. They remark that Haraguchi looks very similiar, but it's hard to tell with the wig and make-up. She flees the bar and into a nearby park where she happens to run into Li again, who is looking at the stars with his telescope. Haraguchi stops, but begins to panic when she hears her pursuers near by. Li puts his jacket around her and they pretend to be a couple making-out in the park, which gets the police off her tail for the time being. Li looks flustered afterwards and apologizing for the action, but she asks him why he's in the park in the middle of the city looking at fake stars. When he doesn't answer, Haraguchi asks why he seems so familiar and Li says they met earlier in the day. She looks nervous, thanks him, and runs off, not seeing the Li mask slip away from Hei's face as he watches her leave.
As it turns out, Haraguchi is the woman Louis mentioned earlier. She ducks into another alleyway, avoiding the police again but is confronted by Jean. Jean claims the Louis told him to "move the stuff" and wants to know where it is. Haraguchi refuses to tell him and when Jean attempts to knock her out, Li somehow shows up in the nick of time and hits Jean over the head with his umbrella. Jean starts to wake up so Li grabs Haraguchi and they run off together.
As the pair cross a bridge over a set of railroad tracks, Haraguchi stops and tells Li to run away from her before something happens to him. But Jean shows up, using his Contractor powers to appear in a concrete pillar next to Li. Jean attacks Li and pushes him off the bridge just as a train passes underneath. Both Jean and Haraguchi assume that's the last of Li.
Haraguchi is taken by Jean somewhere and when she wakes up he informs her that Louis is dead, killed by another Contractor. Haraguchi attempts to escape when the lights go out in the building and the electric lock mysteriously shorts out. She runs again, bumping into a very confused looking Li. He instantly looks relieved, however, and Haraguchi collapses.
A short time later, the pair are heading back to the apartment building. Haraguchi, being carried by Li, remarks on a falling star in the sky, telling Li that it means a Contractor has died. She also explains that the governments are keeping Contractors and Dolls existence a secret and use Gate-based technology to erase the memory of anyone who comes into contact with them. Li remarks that she seems to know a lot about Contractors and Haraguchi explains that she used to work for the National Laboratory and read some things she shouldn't have, but also that her parents were killed by a Contractor when she was young.
They return to Haraguchi's apartment, only to find the entire place ransacked. Li tells her to change clothes and to take what she can, that he'll be next door if anything happens. But Haraguchi has been rattled by the day's events and Louis's death and asks Li not to leave her. They are in Li's apartment when Haraguchi explains a little more detail about her life, that she was waiting for Louis to come take her away. But she realizes now that's impossible. Li asks her what she plans to do no and Haraguchi laughs, saying Louis had all the answers. Li proposes they run away together, he believes it was fate that they met. Haraguchi protests this, saying he shouldn't get caught up in this mess, but Li points out that they already saw his face. Haraguchi asks if she can really trust him, but just then they hear someone enter Haraguchi's apartment. It turns out the police have tracked her to here and begin to search her apartment. Mao provides a distraction so the pair can get away unnoticed.
In a restaurant, Li and Haraguchi discuss their next move. Li says he knows someone who might be able to get them fake passports, but they need a lot of money to do it, asking Haraguchi a leading question about the kind of information she had access to. She says she could get some classified information which could potentially go for a lot of money. Finally, Haraguchi reveals her real name is Chiaki Shinoda (the same woman the police are looking for). Chiaki gets up to use the restroom and Huang uses the moment to slide into the booth behind Li. Huang tells Hei that if he knows where the items are he needs to quit wasting time and get it. Haung leaves Hei to continue his meal but Hei notices some of the Contractors that were with Jean and escapes with Chiaki out the back. They manage to lose the Contractors, but Li is injured in the attack, so they find a place to hide, Chiaki hands over the keys to a train station lockbox.
They arrive at the train station the next day and retrieve a small notebook, but the Contractor team find them once again. Li leaves Chiaki behind and makes off with the book. However, as he flips through it all the pages are blank. The entire thing was a set-up. Hei finds himself surrounded by Jean and his compatriots. They looked rather pleased with luring out the Conractor who killed Louis. Chiaki shows up as well. Hei is quick to remind her that all Contractors are liars and one of Jean's goons makes a move to shoot Chiaki. Hei steps in the way, but the shot that rings out is from Chiaki's gun. It turns out this Chiaki is merely a Doll, a passive medium that they implanted in Chiaki's memories, all part of the ruse to lure Hei out into the open. Hei collapses and the others are sort of dismayed it was this man who killed Louis. The man shoots Hei a few more times, but Mao shows up and tells him that Hei doesn't wear his jacket for a fashion statement; it's bulletproof. Hei makes quick work of Jean's two helpers but when Jean tries to use his Contractor power on Hei Chiaki steps in front of him, taking the fatal blow.
Jean makes his escape and Huang shows up to chide Hei for walking so easily into a trap. He informs the Contractor that the real items were picked up by another Syndicate team and that it should be taken as a lesson. Huang also says Hei should have killed Chiaki once she was no longer useful, calling her a puppet. Hei says she wasn't a puppet, but Mao interrupts the bickering before it can really start. They locate Jean and Hei finishes the job.
Later, back at Li's apartment, the police knock on his door and ask if he knew anything about Haraguchi. Li replies that he hadn't even met her and after showing some I.D., the police leave. Shortly after, Hei hears the call and Wakes into a new city called Nautilus.
Hei has different sides of his personality. First of which is his Li persona. Li is that nice neighbor you know but don't really talk with much. A bland but pleasant person who will often lend a sympathetic ear to your problems, even to strangers. Li appears to show a genuine interest in other people and their hobbies. He gets along well with people that he works with and works diligently. He's not out to cause trouble or rock any boats and mostly keeps to himself. He doesn't talk much about himself if you happen to strike up a conversation with him, nor does he seem to have many friends. People certainly know of Li, but there's nothing specific they could pin down about him. The only hobby Li seems to have is star-gazing, although he doesn't really speak much about that, either.
Li's also easily pushed around, as evidenced in the first episode when he arrives at his new apartment. The landlady assumes Li is a TV repair person and yanks him inside. He goes along with it and only gives a token protest. Again, he doesn't want to cause any trouble, although trouble has a curious way of finding him. Li is prone to panic, at first, but if the situation is severe enough that panic goes away, replaced with a subtle confidence in his actions. He's able to defend himself and others, but without attacking anyone. Kenji asks Li if he's some sort of kun-fu master, which only gets Li really flustered and quickly corrects him by saying it was no big deal.
He's patient with others, though he gets flustered if they compliment him, and kind. Some would consider him to be a bit of a loner, but not in any way a bad person. Certainly not someone capable of hurting anyone. He's a little timid, shy, and personable; the every man's man and the perfect cover persona for Hei.
Hei the Contractor, however, is on the other end of the spectrum from Li. Contractors by their own reputation are rational and calculated, a point that is brought up several times in the show. In the first episode, Hei tells Chiaki that Contractors are monster and liars and this is while he's got his Li persona on. He shows little remorse when the truth comes out later. Hei has little difficulty lying, as it's a means to an end. He's very single-minded, and by extension, selfish. The goal of the mission is paramount, but only if it doesn't conflict with his own; namely information on his sister. In a fight, Hei's calm and collected, calculating his next move but able to adapt as the situation calls for it. Outwardly, he shows little or no emotion, even when brutally interrogating his marks. He's a quick, efficient, and ruthless killer who shows no remorse for taking a life. In a way, this is just another mask he wears, trying convince himself and others that he is a true Contractor in every sense of the word.
But even by Contractor standard's, Hei is odd. It's commented on several times by other Contractors that BK-201 is rather irrational. Havoc, a former member of Hei's team, is able to get Hei angry enough to strike her across the face. He treats Yin as a partner and valued member of the team, whereas Huang constantly remarks that Yin is merely a Doll and nothing more. After a particularly difficult mission, Hei stops by Yin's shop and leaves her a piece of candy and thanks her (I think this is the only time he says thank you in the whole series, actually). Near the end of the series you start to get the sense he considers his teammates to be comrades, although this is never voiced, it's merely through his actions towards them. Otherwise, he keeps his emotions close to the vest and is even more withdrawn than his Li persona.
Hei often acts cold and distant towards others. He's sparse with his words once the Li act has been dropped and has no tolerance for dancing around an issue. He'll get straight to the heart of the matter, even at the expense of whomever he is holding a conversation with, despite how it might make them feel. However, he's not entirely heartless. More than once, Hei has gone out of his way to keep innocent people from harm. In the episode just after the canon point I am taking him from, Hei spends an entire night keeping an eye on a younger girl whom the Syndicate suspects is a special type of Contractor; taking her to an amusement park, for some food, and just talking. It is beyond rational and not something a normal Contractor would waste his time with, knowing that in the end it would be pointless. Another time, the Syndicate has given orders to Hei to kill Huang if he doesn't complete a mission, but once the truth is revealed Hei urges Haung to flee instead, that he would look the other way.
And buried deep under all those layers, there is a part of Hei that is haunted by all the killing he has done. Many Contractors enjoy their work, seizing the opportunity to use their power. It's that very core narture of a Contractor that disgusts Hei, but he persists in it because it's something he excels in, to the point where even Contractors feared him even as a mere human. He continues with the Syndicate for the sake of finding his sister someday. It troubles him, but it's something Hei has driven down so deep in an effort to emulate the very Contractors he hates, that he rarely acknowledges it.
Many aspects of his personality are shown more through his actions than his words, especially his human emotions that he wants to hide away.
Contractor ability: Electrical/molecular manipulation. Hei is able to generate and discharge electrical currents through conductive materials. he's shown several times using the steel wire cable on his belt in this manner. He is able to control the amount of electricity; anything from a mild shock to a lethal dose of electrical current. Hei also uses this to short out electronics and the lights in a building. Later on in the series, Hei is also able to change the very nature of molecules of energy, but this won't be available to him in Wake unless he's ever canon updated that far. Most Contractors have a price to pay for use of their abilities, but it seems Hei is exempt from this rule.
BAMF - No, seriously. Even without his Contractor power, Hei is a force to be reckoned with. He's highly skilled in hand to hand combat and is very athletic. He's also remarkably fast, both physically and in adapting to a situation as the need arises. He's shown more often using his strength and skill as an assassin than using his Contractor ability and was feared even before he took over as BK-201, earning him the nickname the Black Reaper. He uses daggers and a length of steel wire as his weapons.
Eating - Ok, it's not really a power or anything, but it bears mentioning that Hei eats enough for five people in one sitting. Sixteen bowls of ramen are fairly routine. There's no canon explanation for this whatsoever, but it is often commented on by other characters in the show. Most of the time he's caught in the act as Li, who's always flustered when it's pointed out to him. Hei also cooks for himself; usually traditional Chinese dishes.