Xiaoyu Lei

Xiaoyu Lei is a former member of the Heilei and current bodyguard for the Shinoyama Clan. He is presently serving as Sayo Shinoyama's escort while the two of them temporarily live with the impostor posing as Polka Shinoyama.

Appearance
Xiaoyu resembles a child despite being nineteen years of age, sporting short black hair and a youthful face. He wears a long-sleeved top over striped shorts and sock garters. His prosthetic arms and legs are of such realistic, high-quality make as to pass for his natural limbs; meanwhile, though one might assume Xiaoyu wears black short-fingered gloves, his black digits are part of the prosthetic and technological marvels in their own right.

A powerful microphone with long-range sensitivity has been internally integrated into his system, allowing him to eavesdrop on conversations in close and far proximity.

Personality
When introduced, Xiaoyu presents himself as capable, eager-to-please, and humble. Underneath that pleasant demeanor, however, lies murderous intent toward both the Polka impostor and the real Polka Shinoyama. With the former, he presumes the impostor is an inherent threat to the Shinoyama family. His latter grudge against Polka is meanwhile rooted in his own filial worship of Rozan Shinoyama, as he has long been jealous of Polka for being the subject of Rozan's fatherly affections. Over the years, his resentment has evolved into a superior complex wherein he believes he the truly useful son to Rozan and more deserving of the role than the inferior Polka.

Xiaoyu can be extremely stubborn in his suspicions and convictions, intent on doubting if not assuming the worst of the fake Polka even after Rozan says he trusts the impostor. Such stubbornness stems from his personal jealousies and his extreme devotion to the Shinoyamas, both feeding into his need to prove himself as an ideal bodyguard, servant, and 'son'. He is proactive in his goals and extremely suspicious to intense and sometimes comical effect, considering his eavesdropping and frequent late-night activities. To Xiaoyu's credit, his pride and self-confidence allow him to stand his ground against the Heilei and openly reject his blood family.

Background
Xiaoyu is born into the Lei Family, a guild of contract killers known as the "Heilei" with ties to the Shinoyama Group. Trained in the guild's practices from an early age, Xiaoyu is only about nine or ten years old when he is given his first mission: to slaughter a group of small-time terrorists who have threatened the Lei Family, as well as anyone else who happens to be in the target building.

When he arrives, he finds the terrorists dead at the hands of at least three individuals: Majiri, Kana, and Momoya Agakura. When he attempts to cut Majiri's throat, Majiri is charmed by his ruthlessness and cuteness but nonetheless severs his arms and legs in response—though she cleaves them in such a way as to prevent fatal or even major blood loss. When Xiaoyu comes to, she offers to return his limbs someday in exchange for him being adopted into the Agakura Clan.

The Heilei collect Xiaoyu's limbless body and have him treated at a hospital, where he spends his waking days simultaneously bored and scared of what is to become of him. When his father and a girl—possibly his sister Imbi—visit him one day, Xiaoyu overhears the answer: he is to become a "t'ing-fu." Denial sweeps through Xiaoyu, then fear, then murderous rage, feelings which are put on hold when Rozan Shinoyama—whom Xiaoyu is bewildered to hear his father address deferentially—makes an appearance.

Xiaoyu's father explains to Rozan that a "t'ing-fu" is a living child whose body the Lei use to cultivate a poisonous bacteria. Rozan asks if he can purchase Xiaoyu for the sake of outfitting him with the family's latest cyborg technology; though he advises Xiaoyu not to think of him as a generous benefactor, he hopes Xiaoyu will serve as a good companion to the Shinoyamas. His smile is the first Xiaoyu has been given in some time.

Rozan thus takes Xiaoyu in, outfitting him with new limbs as promised, and Xiaoyu devotes himself to Rozan with filial loyalty. The one Shinoyama who does not have Xiaoyu's loyalty is Rozan's second son Polka Shinoyama, another young boy that Xiaoyu disdains as a weakling undeserving of Rozan's affections. Such resentment and jealousy only grow as the years pass—as Xiaoyu continues to watch Rozan act fatherly toward Polka from afar—and he becomes increasingly convinced that he is far more useful and more of a "true son" to Rozan that Polka could ever dream of being.

Present
When Polka is sixteen years of age, he runs away from the family estate. His half nephew Takeru Shinoyama receives confirmation Polka is alive on Day 3 of Corpse God's reincarnated existence; roughly two weeks after Corpse God's reincarnation in Polka's body, the Shinoyamas reestablish contact with "Polka" and invite him to lunch.

The next day, "Polka," Misaki Sakimiya, and Polka-the-shark-plush arrive at the Shinoyama estate for lunch. When Rozan speaks to "Polka" in a private parlor, Xiaoyu is one of three hidden servants guarding the room: one stationed in the ceiling; a second inside; and himself stationed underneath the floorboards. He thus is present when Rozan accuses "Polka" of being an impostor.

Xiaoyu and the other two bodyguards presumably continue to guard Rozan throughout Know's subsequent arson attempt on the estate; they either resume or have remained in their stations by the time Rozan resumes speaking with Corpse God, and, this time, with Misaki. However, when Corpse God requests the hidden bodyguards leave, all three leave at Rozan's command.

That evening, in Rozan's bedchamber, Rozan orders Xiaoyu to escort his granddaughter Sayo Shinoyama to Shinjuku. Xiaoyu immediately assumes Rozan wants him to dispatch the impostor Polka, but Rozan clarifies he wants Xiaoyu to protect Sayo and the fake Polka, whom he believes is not an enemy. Though Xiaoyu is disappointed to be wrong, he sees this as his chance to eliminate both Polkas and agrees to the assignment.

The assignment specifically entails sending Sayo and Xiaoyu to Polka's current residence, a move that is practical for two reasons: both Sayo's and Polka's bedrooms were destroyed in the fire, so she needs a place to stay while the police investigate; second, having a second Shinoyama and a trained guard living with "Polka" will ensure the impostor is kept under close watch.

Xiaoyu is thus introduced to Sayo as her escort, and, once her belongings are packed, accompanies her to her half uncle's Shinjuku residence that night. After exchanging introductions with "Polka's" friends Takumi Kuruya and Misaki Sakimiya, Xiaoyu plays a pre-recorded video of Rozan explaining the circumstances and requesting that "Polka" allow Sayo and Xiaoyu to remain his houseguests for however long the police investigation and room renovations last.

Corpse God agrees. Sayo and Xiaoyu spend the night in the living room and greet Corpse God, Takumi, and Misaki in the morning. As Xiaoyu makes breakfast, he explains he was chosen as Sayo's escort on account of their similar-sounding names; he also reports the Shinoyamas are still entreating with the police. A mattress for Xiaoyu is purchased that day and, when night falls, the group moves Sayo and Xiaoyu into new quarters one floor below the living room: a large room and a tiny connecting side room into which Misaki and Xiaoyu carry his mattress.

Xiaoyu sees Takumi, Misaki, and "Polka" off with a bow. Later, when Sayo is asleep, he eavesdrops on "Polka" conversing with a friend: the friend asks "Polka" what he plans to do with "those two," while "Polka" brings up restarting his fortunetelling business the next day. He also hears a distinct scratching noise. Despite Rozan vouching for the impostor, Xiaoyu reaffirms his distrust in Corpse God and swears to eliminate him and the real Polka should he still live.

The next morning, Sayo and Xiaoyu loiter while Takumi prepares his workstation and Corpse God dons his fortuneteller regalia. Although the Fortuneteller Shop does not open until afternoon, Corpse God receives two unexpected but not unfamiliar visitors: detectives Kōzaburō Arase and Tsubaki Iwanome, the latter of whom requests a fortune reading. Having little recourse to refuse, Corpse God agrees and even consents to Xiaoyu, Sayo, and Arase sitting in on the session.

After Corpse God scries a few facts about Iwanome's personal life, the pencil on the table between them begins autonomously writing something on a piece of paper. Xiaoyu recognizes the scratching noise from the previous night, but it is too dark for him or anyone else to make out the paper's contents—so he is just as shocked as the others when Iwanome crumples the paper, seizes Corpse God's robe, and demands an explanation. Though Corpse God does not give on, Iwanome calms himself down and offers compensation for both the session and wrinkled robe before he and Arase take his leave.

Given Iwanome's abnormal reaction, Xiaoyu figures the paper's contents might be connected to the fake Polka's secret and takes his own leave, using shopping for dinner ingredients and shark merchandise as an excuse to track the officers down. Ever-dutiful, he take care of the shopping first and afterwards locates the detectives exiting a curry restaurant; he then follows them to Youtoukorou and eavesdrops on Iwanome's conversation with Lisa Kuraki. Iwanome accuses Clarissa of passing along information to Polka that only himself and Miyabi Hosorogi should know; Xiaoyu makes a mental note to research Hosorogi's name.

Rest to be added.

Trivia

 * Xiaoyu's surname 'Lei' means "thunder," while 'Heilei' refers to "black lightning."