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 are important to his plans. He is interested in Serena's unknown abilities and also expresses interest in getting a hold of Yuzu's bracelet, stating that she is the "fourth piece" he needs, having already had Yūri capture Ruri and Rin for him.

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.

Yuzu Hīragi
The second character to be known to have dimensional counterparts was Yuzu. Similar 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.