Maximum Mountain (マキシマム
When modern Duel Disks were created, many prototype Duel Disks were abandoned in the mine. Through unknown circumstances, R0, the Mutsuba-style Mobile Duel Device, was also abandoned in a laboratory that was sealed off from the rest of the mine and knowledge of its presence was hinted at in a book in the Goha 6th Elementary library, but was hidden from the Mutsuba family.
When Asana Mutsuba made the decision to Duel Yuga Ohdo and crush Rush Dueling, she decided to use a Maximum Monster against him. Knowing that the previous two Maximum Monsters had been created by rewriting Duel ID cards, she had the Heavy Cavalry Duel Club excavate several Duel Disks from the mine in the hopes that they would find three cards stable enough to be rewritten; eventually succeeding in creating "Wurm Ex-Cavator the Heavy Mequestrian Wyrm", an event witnessed by Goha 5th Elementary's Space Operations Duel Squadron.
Yuga learned of the mine and R0 while researching in Goha 6th Elementary's library and tricked Asana into sending him, Luke, Romin Kirishima, Gakuto Sogetsu, Sebastian, Kaizo, and Ranze and Rinnosuke Nanahoshi to the Abandoned Dorm. From there they escaped into the mine after Yuga sent Kaizo and Sebastian to ask Neiru Saionji about the mine and if he could borrow Neiru's own Maximum Monster; "Yggdrago the Heavenly Emperor Dragon Tree". Neiru sent Kaizo back with Hunt Goto to assist them in finding the mine, which they eventually reached, uncovering several prototype Duel Disks for Yuga to recreate "Super Magitek Deity Magnum Over Road". Asana and the Heavy Cavalry Duel Club arrived soon after and they Dueled a second time, during which "Wurm Ex-Cavator" and "Magnum Over Road" clashed, disintegrating both sets of Maximum cards from the strain, while also exposing the mine to the air due to the energy emitted by the Solid Vision. Yuga eventually defeated Asana and found R0 for her, bringing the Heavy Cavalry Duel Club to accept the idea of modification.
Following Yuga and Asana's second Duel, Hunt returned to the mine hoping to excavate all the Duel Disks and sell the ID cards after converting them into Maximum Monsters. He was discovered there by Goha 66, who made a deal with Hunt to help him excavate the Duel Disks, remaining at the mine after he and Hunt stripped the mine almost completely of Duel Disks. Other parties who had heard of the mine soon set their sights on it hoping to gain Maximum Monsters of their own; Luke brought Hunt to the Abandoned Dorm to ask Asana's permission to dig there, unaware of Hunt's actions, while Braun Honya challenged Asana to a Rush Duel for the right to dig in the mine; Asana settled the matter by having Braun and Luke Duel one another. After the Duel, Luke allowed Braun and his friends to dig in the mine with him, Hunt, Romin and Gakuto, though as Hunt had already stripped the place, only Asana found a Duel Disk, which she extracted the Duel ID card from to give to Yuga at the Goha Rush Duel Team Battle Royal.
- Yu-Gi-Oh! SEVENS episode 39: "Bring it Back! Mutsuba's Pride!"
- Yu-Gi-Oh! SEVENS episode 38: "Unearth the Maximum!"
- Yu-Gi-Oh! SEVENS episode 42: "Space Operations Duel Squadron"
- Yu-Gi-Oh! SEVENS episode 33: "Goha 6th Elementary School"
- Yu-Gi-Oh! SEVENS episode 34: "The Shiatsu Nether-Empire Strikes Back"
- Yu-Gi-Oh! SEVENS episode 35: "Sound! Gohanium"
- Yu-Gi-Oh! SEVENS episode 45: "Upstart Hunter"
- Yu-Gi-Oh! SEVENS episode 43: "Opening! Team Battle Royal"