Underground Cavern

Underground Cavern is a cave located under Yūya's Hideout in the Yu-Gi-Oh! ARC-V (manga). This was where Yūya first arrived in the current era after his father, Yūshō, triggered the World Illusion.

History
Yūya and Reiji went into the underground of Yūya's hideout where Reiji correctly assumed that this is where Yūya first arrived in the current era after his father, Yūshō Sakaki, triggered the World Illusion, something that Yūya confirmed. Yūya revealed that he knew about Reiji and Leo Akaba from his father and when he first heard of Reiji's name in the current era he knew both of them will clash. Yūya asked Reiji do they really need to fight since nothing bad happened between them. Reiji admitted that while this was true, he had sworn to stop Yūya from controlling G.O.D. Despite Yūya's attempt to clear up that his intention is not to control the card, Reiji wouldn't listen to it while reminding the fact that Yūshō was the cause of his father's death. Accepting that fact was inescapable, Yūya accepted Reiji's challenge. Since Reiji refused to use Action Card, Yūya decided to Duel in normal way as he didn't want an unfair advantage. The clash between Yūya and Reiji's monsters caused a huge distortion in space. Before the Duel can end, however, Yūya noticed a camera hidden nearby and asked Reiji to let him prove his story, but to his surprise, Reiji already knew about the third party besides them because that third party saved him when World Illusion began as Reiji exposed the camera. Yūya demanded their observers to show themselves and questioned their identities. As demanded, Ren appeared before them and introduced himself with Yūto and Yūri confirming that he was the one who infiltrated Yūya's memories. Ren then revealed that both Yūya and Reiji possessed The Adam Factor, a power necessary to awaken G.O.D together with The Eve Factor, and one day they will take that power from them. Before the conversation could go further, the underground started to collapsing from the impact of the earlier clash, forcing Yūya and Reiji to let Ren go and escaped to safety by riding on "Phantasma Dragon" and "Zero Laplace" respectively.