Underground Waterway

Underground Waterway is a sewer located at Maiami City' South District in the Yu-Gi-Oh! ARC-V (manga). This was where Yūya trained to maneuver a D-Wheel for two weeks.

History
When Yuzu looked for Yūya, Shingo told her that he heard some kids talking about strange noises from a manhole in the south district of Maiami City. Yuzu reached the manhole Shingo mentioned, went into the sewer to find Yūya on a D-Wheel. Yūya explained to Yuzu that he spent the last two weeks training uninterrupted in the underground waterway to get stronger to face his enemies, though Yuzu was curious why Yūya did it on his own instead of getting help from Yūgo. Within Yūya's mind, revealed to be the one training Yūya to use a D-Wheel, Yūgo is confronted by Yūto and Yuri over why he pushed Yuya. Yugo explained his reasons to be the assumption Yūri had made: That the awaken The Adam Factor with Yūya was gradually disrupted their link to Yūya. Thus Yūgo intended to teach Yūya his skills in case he ended dueling on his without them to back him up.