Fusion Dimension Arc

Fusion Dimension Arc (融合次元編 Yūgō Jigen Hen) is the fourth sorry arc of Yu-Gi-Oh! ARC-V anime series. It follows Yūya and his friends infiltrating Academia to save Yuzu and her counterparts, and put an end to Leo Akaba's ambition to unite the four dimensions. There are two opening and ending themes used in this arc. The first opening and ending are LIGHT OF HOPE by Unknown Number!!! and Vision by Kuso Iinkai from episode 112 to episode 124, while the second opening and ending are Pendulum Beat! by SUPER DRAGON and Dashing Pendulum by M!LK from episode 125 onwards.

Ambush at You Show Duel School
With Yūri's attack, Asuka proposed to Yūshō that they should attack Academia now while they have the chance. Yūshō agreed with her suggestion and was about to prepare, but Dennis and a squad of Academia Duelists arrived, finding their location based on several witnesses' testimony. Dennis, who was revealed to be Yūshō's former student, challenged Yūshō to a Duel, which Yūshō accepted. Yūshō used his Trap card to distract Dennis and bought some times for him and his students to escape from them, going to the harbour. On their way to the harbour, Yuzu and Yūgo were surrounded. Before they could Duel, Yūgo got transported by Yuzu's bracelet due to Yūya and the others' arrival. Dennis tasked Isao, who bear a grudge against Yūya over his defeat during Maiami Championship, to deal with Yūya, while Dennis chase after Yūshō with Kaito following him in tow.

Yūya vs. Isao
Gongenzaka and Shingo protected Yuzu, allowing Yūya to concentrate on Dueling Isao. Learning from his previous defeat, Isao utilised his newfound power to Fusion Summon Level 12 Fusion Monster "Shura the Supremacy Star" that damaged himself but also strengthened his monster based on the Level of its own and Yūya's monster, which doesn't apply to Xyz Monster that doesn't have any Level. He also prevented Yūya from getting any Action Card by attacking him directly like before, but Yūya this time able to dodge most of Isao's attacks thanks to the roller skates he received from Allen. Yūya also countered "Shura's" effect by giving Level to "Dark Rebellion Xyz Dragon" and eventually cornered Isao. Refusing to admit defeat the second time, he attempted to force the Duel into a tie, but Yūya managed to save both himself and Isao using his trap card, "Acrobat Tower" and defeated Isao after winning the gamble from the trap card. Isao lamented over his second lost, but as he watched how the audience were impressed and clapping for their Duel, Isao acknowledged that Yūya's Entertainment Dueling is not as bad as he believed it to be, much to Yūya's happiness.

Kaito vs. Dennis
Dennis caught up to Yūshō and Asuka just as the ship left the harbour and demanded for their Duel to be continued. Kaito interrupted and took the challenge in Yūshō's stead, and the two begin the Duel. Dennis has advantage in the Duel with the combination of his Fusio and Xyz Entermage monsters since he already knew Kaito's deck based on the data gathered by Academia who placed a bounty on him for defeating many of their Duelists. However, Kaito able to turn the tide when he summoned "Little Fairy", Sayaka's card that she has entrusted to him and was not on his data. Using the fairy's effect, Kaito performed Rank-Up Xyz Summon, summoning "Neo Galaxy-Eyes Cipher Dragon" and won the Duel. Yūshō invited Dennis to join him so they can change Academia together with their Entertainment Dueling. Dennis, however, declined his offer, feeling that he has not right to return as their comrades after betraying Yūya, Shun, and the Lancers. As he slowly walked backwards to the edge of the ship, Dennis revealed where Ruri and Rin were being held captive. Now he couldn't return to Academia as he has betrayed the Professor by revealing his secret, Dennis sealed himself into a card as a form of redemption, much to Yūshō's dismay who then kept his card.