Xiaoyu Lei

Xiaoyu Lei is Sayo Shinoyama's escort, and an alleged 'butler-in-training' for the Shinoyama Clan.

Appearance
Xiaoyu is an adolescent with short black hair and a youthful face. He wears a long-sleeved top over striped shorts, sock garters, and black-fingered gloves.

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. Such sentiments are fueled by Xiaoyu's devotion to Rozan Shinoyama: he believes the impostor is a threat to Rozan and the Shinoyama Clan; and he resents the real Polka for being an 'inferior son', believing himself to be the 'truly useful son' of the two.

Background
Xiaoyu is born into the Lei Family, a guild of contract killers known as the "Heilei" with ties to the Shinoyama Group. and trained in the guild's practices from an early age. He is still a boy when they send him out on his first job—a job which results in him losing all his limbs after he encounters an individual named 'Agakura'.

Xiaoyu spends his waking days at the hospital scared of what is to become of him and utterly bored, unable to do anything else but stare at the ceiling. When his father and another child come to visit him, he overhears his father say that he has no chance of recovery and that they will make him into a "t'ing-fu." Denial courses 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 with -sama—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, and that he has no qualms turning his own son into one. Rozan asks if he can buy Xiaoyu off him and outfit Xiaoyu with his family's latest technology, and then tells Xiaoyu not to think of him as a generous benefactor—he claims he sixmply needs a test subject to be his newest cyborg. Still, it is with a smile that he says he hopes Xiaoyu will be a good companion to his family—and Xiaoyu cannot remember the last time someone smiled at him.

Rozan thus takes Xiaoyu in, outfitting him with new limbs as promised, and Xiaoyu devotes himself to Rozan and the Shinoyamas from then on with filial loyalty. His devotion does not extend to Rozan's second son Polka Shinoyama, whom he considers a weakling undeserving of Rozan's affections. Such resentment and jealousy only grow as the years pass and he continues to watch Rozan act fatherly toward Polka from afar, and he becomes increasingly convinced that Polka is no 'true' son of Rozan's—not when Xiaoyu would be far more useful of a son than Polka could ever dream of being.

Present
In the immediate aftermath of the arson attack on the Shinoyama manor, the Shinoyamas assign Xiaoyu as Sayo Shinoyama's escort with orders for the two to move in with Sayo's uncle Polka. At face value, this move is largely innocuous: as the fire destroyed both Sayo and Polka's rooms, Sayo needs a place to stay. However, Xiaoyu appears to be no mere butler-in-training; he has orders from above to keep an eye on "Polka"—or rather, the impostor posing as Polka.

Xiaoyu and Sayo arrive at "Polka's"—the Corpse God's—residence that night, and exchange introductions with Polka's roommates Takumi Kuruya and Misaki Sakimiya. On Sayo's behalf, Lei explains that Sayo's room was destroyed and procures a pre-recorded video from Rozan, in which Rozan requests that Polka allow Sayo and Xiaoyu to stay with him for the time being.

The Corpse God agrees, and Sayo and Xiaoyu spend the rest of the night in the living room (with Xiaoyu claiming that he is able to sleep on his feet). Sayo is still gloomy while Lei is chipper come morning, and Xiaoyu apologizes on Sayo's behalf to "Polka" and his friends after they file into the living room.

"Polka" asks Xiaoyu how he came to be Sayo's escort; Xiaoyu, as he sets a pan and portable stove on the table, claims he was chosen because his name sounds similar to "Sayo." When "Polka" follows this with an inquiry into the welfare of the Shinoyamas, Xiaoyu cracks an egg into the pan and—after telling "Polka-sama" not to speak to deferentially—replies that the Shinoyamas are still busy dealing with the police.

As nighttime approaches, Xiaoyu and Sayo move into connecting rooms a floor below the others' main living space. Sayo claims the larger room while Misaki helps Xiaoyu carry a mattress inside, with Takumi and "Polka" looking on. Xiaoyu moves the mattress into the tiny side room, and bows deeply when the others bid him and Sayo good night.

Later, when Sayo is asleep, Xiaoyu listens in on "Polka's" conversation with one of his friends via electronic means: the interlocutor asks "Polka" what he plans to do with 'those two', and "Polka" mentions restarting fortune-telling the next day.

Trivia
Smiling at his success, Xiaoyu clenches his fists and vows to expose "that damn Polka Shinoyama impostor" regardless of his master's decision to trust said impostor. He intends to eliminate the impostor if his master will not—and then the real Polka, if he proves to still live.
 * Xiaoyu's surname 'Lei' means "thunder," while 'Heilei' refers to "black lightning."