Dimensional Counterparts

A dimensional counterpart (似た者同士 Nitamono dōshi, lit. Fellow look-alike) is a phenomenon featured in the Yu-Gi-Oh! ARC-V anime, in which a person from one dimension resembles another person from another dimension. In addition to sharing the same face, the counterparts seem to be drawn to each other for an unknown reason.

History
Accordingly to Reo Akaba's actions, it is hinted that these counterparts, the girls in particular, are important to his plans. For this purpose, he locked up Serena inside the Academia Castle for most of her life and ordered Yūri to bring the other remaining girls, Ruri, Rin, and Yuzu. Each of this girls bears uncanny resemblance with each other and possesses a bracelet with special powers that is connected to the boy dimensional counterparts, Yūya, Yūto, Yūgo, and Yūri.

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:

Yūya Sakaki
Yūya was the first character to have a dimensional counterpart. Each of these counterparts has a Dimensional Dragon and also can enter a rampant state of mind, which has been given the title "Berserk Mode" by fans. They are also able to sync with each other as well. These unique abilities drive subconsciously drives them to completely combine with each other.

Yuzu Hīragi
The second character to be known to have dimensional counterparts was Yuzu. Similarly to Yūya and his counterparts having Dimensional Dragons to help signify themselves as counterparts, Yuzu and her counterparts wear unique jeweled bracelets, which have mysterious abilities. For this reason, they are collectively called Bracelet Girls (ブレスレットの Buresuretto no Ko).