Allen Kōzuki

Allen Kozuki  (アレン, Kōzuki Aren) is a character in the Yu-Gi-Oh! ARC-V anime. He is a friend of Sayaka Sasayama and is a surviving resident of the Xyz Dimension.

Past
Prior Academia's invasion, Allen and Sayaka were student from Heartland Duel School's Clover branch, the same branch Kaito studied. He was also one of Yūshō's pupil.

When Academia attacked, Allen and the other from Clover branch tried their best to survive, but they eventually overpowered and were forced to be in hiding.

Yūya vs. Kaito
Allen and Sayaka reunited with Shun, who got transported back to Heartland with Yūya, Shingo, and Gongenzaka. The three of them then looked for Yūya and the others and met the refugees that Yūya and the others had saved before who told them their location, arriving in time to stop the Duel between Yūya and Kaito before it was too late. Along with Shun and Sayaka, Allen assured Kaito that Yūya and the others are allies, expressing his gratitude that bringing three new allies was extremely helpful for them. Despite these assurance, Kaito still refused to fight together with them and left the scene.

At their hideout, Allen introduced himself and Sayaka as he told Sayaka not to overwork herself. He then commented on Yūya's resemblance with Yūto, thinking that he was in fact Yūto himself, but Shun cleared this confusion. Allen then revealed that while Yūto and Shun were gone, the Academia had launched a massive offensive attack, wiping out Resistance's Spade and Clover branches, forcing them to be in hiding. Their conversation was cut short when Sayaka questioned Yūya's connection with Yūshō, and the latter revealed that Yūshō is his father. Hearing this, Allen explained that Yūshō was their teacher and had abandoned them during the invasion, shocking Yūya.