Dimensional Counterparts

A dimensional counterpart (似た者同士 Nitamono dōshi, lit. Fellow look-alike) or also known as reincarnation (分身 Bunshin, lit. Avatar or Fragment) is a term featured in the Yu-Gi-Oh! ARC-V anime, in which a person from one dimension greatly resembles another person from another dimension. In addition to sharing the same face, the counterparts are drawn to each other due to their connection with certain two individuals, Zarc and Ray, who are later revealed to be their original incarnations.

Origin
Before the existence of the Four Dimensions, there's a world where all summoning methods existed, which is known as the Original Dimension. In this dimension, lived two individuals: the Duel Champion and superstar, Zarc, and Leo Akaba's daughter who is also a professional Duelist, Ray. As Zarc reached the top of Dueling world, his thirst to attain god-like power and the dragons' resentment towards humanity drove him to destroy the world together with his Four Heavenly Dragons. He was stopped by Ray who used four cards and Dimension Bracelets created from Earth's natural energies. The clash between them caused each of their bodies and souls to be split into four fragments and each were reborn in the newly existed four dimensions. Zarc's fragments are: Yūya Sakaki, Yūto, Yūgo, and Yūri. Ray's fragments are: Yuzu Hīragi, Serena, Rin, and Ruri Kurosaki. Leo's plan, Revival Zero, is fusing the four girls so he can revive Ray.

Fifth Dimension ARC-V Arc
Both counterparts eventually became one following Leo's plan: Ray's counterparts were all transferred into the ARC-V Reactor that Leo created to revive Ray using the carded people's life energies and the girls became one within the reactor's core. However, the life energies were insufficient, leaving Ray's resurrection incomplete and could only take corporeal body. Meanwhile, Zarc's counterparts were fused after Zarc took control of their bodies and was fully revived, continuing his rampage to the world. By borrowing Reira Akaba's body, Ray defeated Zarc the same way she did before. However, in the process of the dimension split, Reira drove out Ray's soul from her body and sealed Zarc's evil soul into her own before he could reincarnated into four dimensions again.

As the result, Ray and her counterparts' souls disappeared with Ray's body still inside the ARC-V Reactor's core without any sign of life, while what remains of Zarc was revived as Yūya, his main host, with his other reincarnations' soul residing within the boy due to Reira's action prevented them from splitting. Zarc's evil soul, who was imprisoned inside the infant Reira rendered the baby into catatonic state and slowly trying to take over the body. However, watching Yūya's Entertainment Dueling gradually reminded Zarc of his long lost passion to bring happiness with his Dueling and eventually pacified his soul. Following Yūya's victory against Reiji, Ray reacted from within the ARC-V's core and then transported herself and Yūya's friends and family to Pendulum Dimension where she revived Yuzu with the rest other counterparts residing inside her before she and Zarc passed on.

Mistaken Identities
A common recurrence is for a character to confuse one counterpart with another counterpart due to their identical facial structures. Instances of confusion include:

Zarc
Zarc is known as the Demon Duelist and Supreme King Dragon Zarc,  who once nearly destroyed the whole world undefined  and caused it to be split into four dimensions. After his defeat, his soul were split into four together with the original dimension and these four souls reborn as four boys who each resides in each four dimensions. Like Zarc, each of his counterparts has a Dimensional Dragon   and their connection with Zarc allows them to synchronize their mind with each other. Zarc, who still seeks destruction, constantly influence Yūya and his counterparts through a rampant state of mind called The Awakening that usually triggered when they are greatly angered or the dragons are summoned at the same place and time. By entering this state, Zarc slowly tries to consume their souls so he can be reborn.undefinedundefinedundefined Each of the counterparts are capable of absorbing one another. This can be done in two ways: Willingly becoming one with the other as in Yūya and Yūto's case or the counterparts Duel and the loser will be absorbed as seen with Yūri absorbing Yūgo.undefinedundefinedundefined With his incarnations now one in Yūya's body, considering them his "alter egos" rather than actual people, Zarc took complete control over Yūya, turning his body into a demonic form. While in control, Zarc defeated everyone who faced off against him using demonic versions of his dragons and his own dragon form. However, while fighting Ray as she used Reira Akaba's body to duel him, his incarnations rallied under Yūya and resisted him long enough to cause his defeat while exposed to the En Cards. However, instead of being separated from each other, Yūya and his counterparts remain in one body after Reira extracted Zarc's essence from them.

Ray
Ray is the girl who stopped Zarc from destroying the whole world and her soul were also split into four dimensions. Similarly to Zarc's counterparts having Dimensional Dragons to help signify themselves as counterparts, Ray's counterparts are wearing unique jeweled bracelets   that contains Earth's natural energies. For this reason, they are collectively called Bracelet Girls (ブレスレットの Buresuretto no Ko). Their Decks are also created from the four cards with the same natural energies that Ray used together with the bracelet to defeat Zarc. These decks are based from Japanese proverbs, Kachō Fūgetsu  which literally means: Flower, Bird, Wind, Moon. The bracelets they possessed became some sort of radar, the gems will glow if Zarc's reincarnations are in one place and about to become one. In Yuzu's case, her bracelet has an ability to transport Zarc's reincarnations to prevent them from gathering in one place, most likely to stop Zarc's revival. All four girls were briefly placed under the control the Doctor's Parasite Monsters, making them temporary antagonists,    but were freed when Leo carded the Doctor for his dangerous thinking. However, they were already placed in capsules to be inserted into the reactor core of ARC-V. Leo, not regretting their feelings as separate beings or taking Ray's wishes into account, inserted them into the reactor to be forcefully merged back into Ray. However, Ray lacked a physical form and was forced to use Reira's body to deal with Zarc once he was reconstituted. However, once Zarc was defeated, Ray was forced out of Reira's body as the child used the En Cards to extract Zarc from his incarnations and absorbed it. When Ray returned to ARC-V, Leo deduced that his daughter and her incarnations are an inactive state following the second dimensional split. But upon sensing Yūya's victory against Reiji enabling Zarc's spirit to finally rest, Ray awakens and reincarnates as Yuzu with her counterparts' spirits residing within her.

Trivia

 * In Japanese, both male and female Standard and Fusion dimensional counterparts are sharing same voice actor/actress. The male Standard and Fusion counterparts are voiced by Kenshō Ono, while the female are voiced by Yūna Inamura.
 * In English Dub version, all the male dimensional counterparts are voiced by Michael Liscio Jr..
 * In English Dub version, all the female dimensional counterparts are voiced by Emily Bauer.
 * The Fusion dimensional counterparts are the only ones who have no relation with each other.