Moon Child is a movie starring Gackt Camui (formerly Malice Mizer) and Hyde (L'Arc~en~Ciel), Zeny Kwok and Wang Leehom (Lee-Hom Wang). It is set in the world of the near future, where an orphan and a vampire form a friendship that is put to test by a gang ravaging the city. In this movie, Sho (Gackt) falls in love with a girl named Yi-Che, who was mute since she was little, and in turn she falls in love with Kei (Hyde). This story takes place in a fictional city called Mallepa. It was filmed in Taiwan.
In the year 2014, Japan suffers a major economical collapse and people are forced to emigrate to nearby mainland China. In the mainland there is a city called Mallepa, where living conditions are stable. In this city three young orphans — Sho (Gackt), Shinji (Sho's older brother) and Toshi, around the ages of eight to twelve — sustain themselves through pocket-picking and other petty crimes. While robbing a gangster, Sho meets Kei (Hyde), a vampire on the brink of death. Sho saves him and in return, Kei saves the orphans from the gangster, who bursts into their hideout demanding the return of his money. Shinji is shot in the leg and carries a limp through the rest of his life. During the rescue, Shinji and Sho find out about Kei's vampiric nature, but they do not seem to mind.
The movie jumps forward in time to Sho as a young man. While the three orphans still live on robberies and thefts, they have graduated to gun-wielding chaos that makes for dramatic fire fights. Kei is still with them and serves as a mentor to Sho, now grown up. Shinji has a limp and is a drug addict. Now it is their friend Toshi who helps Sho and Kei in their thievery.
While performing a robbery one night, Sho, Kei and Toshi meet an enraged Taiwanese man, Son (Wang Lee Hom) and make a quick decision to unite with the stranger. Later, they learn that Son was taking revenge on the gang that Sho and company were trying to rob because they had raped his sister, Yi-Che, who has refused to talk since the incident. Sho, Toshi and Kei meet Yi-Che and the group merges into an admirable friendship. Along the way, Sho develops feelings for Yi-Che but the matter is complicated as Yi-Che's interests rest with Kei.
The tension created by the common romantic interest of Sho and Kei, two best friends, makes for heart-wrenching anguish. Kei is unable to reciprocate Yi-Che's love and voices his demons in bitter soliloquies regarding his cursed immortality, the highlight of an admirable performance by amateur actor, Hyde.
The peace is broken as Toshi is kidnapped and killed by gangsters. Kei claims revenge but is apprehended by authorities and kept in an undisclosed prison. We learn that nine years pass in this manner. Son, having witnessed Kei's killing of the gangsters, abandons his friendship with Sho for a place with the Taiwanese mafia that killed Toshi. Sho has married Yi-Che and the pair have a young daughter, Hana. On the news one day, Sho, now a prominent mafia boss, sees reports about Kei in prison, describing him as "the modern day vampire." Sho visits him and finds his friend a lawyer, but Kei is mostly unresponsive.
Meanwhile, back in Mallepa, Shinji is killed by Chan, the Taiwanese mafia crime boss whom Son follows. Son and Sho go to view his body and the brothers-in-law fight over his death. Sho threatens to kill Son's entire family, conveniently forgetting that his wife is Son's sister. The fight dissolves into an emotional peak and Sho draws his gun on Son. Yi-Che speaks for the first time, pleading with them to stop. She finally convinces her brother and husband to stop fighting, for the moment.
Soon after, Yi-Che is hospitalized for her brain tumor. During Son's visit, it's revealed that the tumor is affecting her cognitive abilities and that she doesn't have much time left. She directs her daughter, Hana, to greet Son as her grandfather. She refers to Sho as "Kei," provoking some painful realizations for her husband. With his brother dead and his wife dying, Sho again turns to his childhood friend and mentor, Kei, but his phone call reaches Kei while the vampire is on his way to death row and leaves Sho in greater despair and loneliness.
Luckily, the phone call revives Kei's will to live and he breaks free of the transport truck to return to Sho. Sho pleads with Kei to transform Yi-Che into a vampire to save her from death, but Kei refuses, prompting another emotional speech laden with self-loathing. He would rather let Yi-Che die than force her to live a vampiric half life, and he calls Sho "selfish" for wanting Yi-Che to live without regard for the life she would have to endure as a vampire. Sho then requests that Kei help him exact revenge on the mob that killed Shinji. Kei accepts, albeit reluctantly.
The two head to the rundown warehouse where they met and a dazzling firefight ensues against Chan's Taiwanese mob goons. It becomes obvious that Sho doesn't intend on surviving when he asks Kei to promise to watch over Sho and Yi-Che's daughter, Hana, before they dive into the fight. Predictably enough, Sho fights without regard to his own safety, prompting painful protests from Kei. Finally, the pair meet up with Son.
Sho considers Son a traitor for joining the gang that killed Toshi. He also seeks revenge for Shinji's death. Because of these personal reasons, he keeps Kei from following him by shooting the ceiling of the warehouse so that beams of light shine over the entire floor except for a small corner that Kei occupies. Because of his vampiric nature, sunlight is fatal to Kei and he is left behind as Sho and Son head to their own match rife with the tension of personal grudges.
The shooting continues until each man is left with only one bullet and they decide on an old-fashioned duel with the agreement that the survivor takes care of remaining relatives, namely Hana, Sho's daughter and Son's niece. The rules are to face away from each other and shoot on the count of three, but after whirling around, only one shot sounds. Sho falls to the crumbled floor of the warehouse, fatally wounded as Son is left with the realization that Sho spared him on purpose.
Meanwhile, the leader of the Taiwanese gang, Chan, is betrayed and killed by his two young apprentices. They come across Kei, still in the corner, and shoot him repeatedly. Kei takes the painful shots, sliding, presumably dead, down the tiled wall to the floor. The two teenagers turn away to leave but due to his vampiric ability to heal, Kei has recovered, and now, no longer concerned for his own safety, runs through the beams of sunlight. He shoots and kills the two ruthless teens and runs off to find Sho.
Kei stumbles into the clearing to see Sho dying on the ground and Son with the smoking gun. Son seems to repent for his actions. Although he has no bullets left, he raises his gun towards Kei, prompting a furious return as Kei shoots Son repeatedly, with fury in his eyes. The man dies as Kei rushes to Sho.
During a touching death scene, Sho grasps upward with a bloody hand while Kei cradles him protectively. All the tension between the two is forgotten and Kei is left with only the sadness of having lost his only friend. The lights dim on the tragic scene.
The movie then skips again to Hana, eighteen and grown up, unveiling a repainting of her mother's original mural. Kei, like a proud parent, congratulates her and sends her off to study abroad. When he returns to the mural, he finds Sho, standing in front of the mural which Hana revived.
Unable to face the loneliness, Kei had turned Sho into a vampire, but Sho was unable to face what he had become and could not let his daughter see him, so he had stayed away while Kei fulfilled his promise to raise Hana.
With responsibilities towards Yi-Che's daughter fulfilled, Kei and Sho drive off to the beach where they and Toshi, Son, and Yi-Che had bonded as friends. The pair of life-weary vampires, the only two left of their original group, commit suicide. In the afterlife, the original group meet again like they were when they first met: as friends.