Hei is a tall, slender young man with black hair and dark blue eyes. His appearance shifts notably depending on the identity he assumes. In his civilian guise as Li Shengshun, a mild-mannered exchange student, Hei dresses casually typically wearing a white button-down shirt with rolled-up sleeves, blue jeans, gray sneakers, and a forest green hooded jacket. This unassuming look allows him to blend easily into everyday environments.

When operating as a Contractor, Hei adopts a more tactical appearance. He wears a black bulletproof trench coat with a high collar and a lime green inner lining, along with a black tactical harness, matching pants, gloves, and a sweater. He also wears black combat boots and conceals his identity with a distinctive white pierrot-style mask, marked by red lips and a purple thunderbolt design over the left eyehole.

Following the traumatic events at Hell’s Gate, Hei’s appearance becomes noticeably disheveled. He grows his hair out, stops shaving, and his signature trench coat becomes worn. His mask is visibly damaged, and he frequently appears in a dark ski jacket, reflecting his more unstable state during this period.

After traveling with Suou Pavlichenko and honoring his vow to stop drinking, Hei regains a more composed appearance. He cuts his hair, shaves, and eventually returns to his traditional “Black Reaper” attire, resuming his role with renewed focus and clarity.

Hei is a complex individual whose personality shifts depending on the roles he adopts. While operating under the alias Li Shengshun (李生舜, Lǐ Shēngshùn), he portrays a polite, timid Chinese exchange student who is eager to help others but largely keeps to himself. This false persona serves as a cover for his true identity and activities as a Contractor.

In his true form as Hei, he is a highly skilled and calculating assassin, known for his strategic thinking and unwavering determination. Unlike most Contractors who are believed to be emotionless Hei frequently displays a wide range of human emotions. He is deeply empathetic, capable of forming strong attachments, and is driven by personal convictions. His loyalty and affection for his younger sister, Bai, serve as a major motivator behind many of his actions, particularly his search for her following her mysterious disappearance.

Despite his often cold and tactical mindset, Hei retains certain human quirks, such as a remarkably large appetite, which regularly surprises those around him. He is also notably stubborn; once committed to a goal, he pursues it relentlessly, even if it means taking irrational risks.

A significant shift in his personality occurs after the disappearance of Yin, a close companion. Believing he was responsible for her presumed death, Hei falls into a state of depression and emotional instability. During this time, he begins drinking heavily, becomes increasingly short-tempered, and exhibits violent outbursts most notably toward Suou Pavlichenko, whom he slaps on multiple occasions during moments of frustration. This darker phase marks a stark contrast to his previously composed nature.

However, after spending more time with Suou and seeing parts of himself in her, Hei gradually regains control of his emotions. He eventually returns to his more focused and compassionate self, reconnecting with his core principles and abandoning the destructive behaviors that had taken hold of him.

Before awakening as a Contractor, Hei was a compassionate and protective older brother who took on the role of guardian to his younger sister, Bai, despite being quite young himself. Their lives changed dramatically during a meteor shower event that triggered Bai’s transformation into a Contractor granting her the ability to manipulate matter at a molecular level. With her newfound powers, Bai became the original holder of the BK-201 designation and was soon recruited into the Syndicate.

Although Hei had a natural aversion to killing, he chose to become a mercenary to remain close to his sister and protect her. His exceptional combat skills ranging from martial arts proficiency to tactical improvisation and agility quickly made him a feared figure on the battlefield, earning him the moniker “The Black Reaper.” However, as the war surrounding Heaven’s Gate intensified, Hei became increasingly disturbed by Bai’s actions and the moral cost of their missions. Despite fleeting thoughts of stopping her by force, his deep bond with Bai ultimately prevented him from taking action against her.

During the conflict known as the Heaven’s War in South America, Bai and the rest of Hei’s team mysteriously vanished. Unbeknownst to Hei, Bai had merged her consciousness and powers with him during the final moments of the conflict, passing on her Contractor abilities and causing the BK-201 star to become associated with him.

After Bai’s disappearance, Hei continued to operate under the Syndicate, driven by the desire to uncover the truth behind Heaven’s Gate and learn what truly happened to his sister. He also shares a complex past with Amber, a former Syndicate comrade and current leader of the rogue organization Evening Primrose, whom he seeks out in the hope of unraveling the secrets that tie them all together.

Hei is one of the most formidable figures in the Darker than Black universe, combining elite combat training with the deadly precision of his Contractor abilities. Even without supernatural powers, Hei is highly dangerous due to his physical prowess and tactical mind.

Physical Abilities

Peak Human Condition
Hei possesses exceptional agility, speed, reflexes, strength, and endurance, allowing him to evade detection, scale structures, and escape tight situations with ease. He frequently moves without making a sound, disappearing from sight before onlookers can react, a trait that makes him highly effective in infiltration and assassination.

Expert Hand-to-Hand Combatant
Hei is a master of martial arts and acrobatics. He is capable of performing backflips, mid-air cartwheels, and other complex maneuvers with minimal effort. His close-quarters combat ability is refined enough to allow him to subdue other Contractors, even when not relying on his powers.

Skilled Tactician
Hei demonstrates keen battlefield awareness and improvisational skill. Since his Contractor ability requires direct contact, he often depends on surprise tactics to gain the upper hand. His intelligence and adaptability are evident in encounters such as his strategic duel against Wei Zhijun, where his creativity and unpredictability secured victory.

Contractor Power

Electricity and Molecular Manipulation
Hei’s Contractor ability allows him to generate and discharge high-voltage electricity through conductive materials, such as water, metal, or wires. He often channels this energy through his knife or surrounding surfaces to incapacitate or kill targets instantly. The power is not limited to static discharge; Hei demonstrates a sophisticated command over electrical flow, capable of disrupting infrastructure and disabling multiple systems simultaneously.

In addition to electricity, Hei’s power originally belonging to his sister Bai grants him advanced molecular-level manipulation. Though rarely explored in full, this ability theoretically allows for the alteration of gate particles and matter at the quantum level, making it one of the most coveted and potentially dangerous Contractor powers known. This latent function of his ability underlines his uniqueness, as he is technically still human and gained these powers through Bai’s fusion with him during the Heaven’s Gate incident.

Meteor Fragment Amplification
While in possession of a Meteor Fragment, Hei’s abilities are significantly enhanced. During the Heaven’s Gate incident in South America, this amplification allowed him to unleash devastating levels of destruction, including the near-erasure of large geographic regions though the specifics remain classified within the series.