Yūgo/Relationship

Rin
Rin is Yūgo's childhood friend. They both are orphans who grew up together. Both shares the same dream to Duel Jack Atlas one day, building Yūgo's D-Wheel together. Rin acts like a mother for Yūgo, always scolding him for his recklessness and short temper that often gets him into trouble, which sometimes annoys Yūgo. It was shown that Yūgo harbours feelings for Rin, blushing and grinning happily when Yuzu thought that Rin was his girlfriend. His affection for Rin is also expressed when Yūgo attempted to hug Yuzu or Serena because he mistook them for Rin. While it was still unknown whether Rin return his feeling or not, both are clearly close to one another. Yūgo's feelings for Rin is what driving him to find Yūri and save Rin.

Yuzu Hīragi
Yuzu was saved from Yūri by Yūgo, who mistook her for Rin. When they were in the Synchro Dimension, Yūgo and Yuzu built a quick friendship. Yūgo attempts to help out Yuzu with the issue of the Interdimensional Domination, such as trying to warn the citizens about the Fusion Dimension and getting annoyed when others laughed at her, he also signed her up for the Friendship Cup, believing it would be a good idea to convince others about the threat. Yuzu also shows concern for Yūgo and able to relate herself with him because of the absence of their mother in their lives. However, she has been frequently annoyed by Yūgo, due to him constantly mistaking her for Rin and his straightforwardness, causing her to hit him with her fan, or threatening to do so. When Yuzu lost against Sergey and crashed into a building, he was horrified, crying for her as he determined to continue her wish. When he reunited with her and found out she is still alive, he was so relieved and happy that he tried to hug her. This is the first time he tried to hug her without mistaking her as Rin, which also showed how much he cares for her as a friend.

Yūto
Yūgo had an antagonistic relationship with Yūto and he travelled from one dimension to another to find him so he can defeat him. Their animosity towards each other was strong enough to make them act first before thinking further. This turned out to be a misunderstanding between the two of them. Yūgo mistook Yūto as Yūri, who kidnapped Rin, while Yūto mistook Yūgo as one of Academia Duelists when the latter challenged him instead of answering his question on their first meeting. After the misunderstanding between them are cleared and now they are residing inside Yūya, their relationship significantly improved and the previous hostilities between them were all forgotten. Both now willing work together to support Yūya, and Yūgo even gave his encouragement to Yūto when it was his turn to assist Yūya with Yūto accepting it.

Yūri
Yūgo bears strong hostility towards Yūri, who was responsible for kidnapping Rin. He continuously hunts him down, traveling from one dimension to another to find him. When he mistook Yūto for Yūri, he immediately challenged him without thinking further, showing how much he resents him. Yūgo's hostility towards Yūri was strong enough for him to chase after the latter right after his match in Friendship Cup even at the risk of being disqualified. And when they meet again in the Academia, Yūgo put aside his goal of rescuing Rin and leaving it to Edo Phoenix just to beat Yūri up. His animosity towards Yūri increased further when Yūri purposely teased him by mistaking his name not only once but twice. Yūri, on the other hand, doesn't return Yūgo's hatred and initially only saw him as a nuisance that doesn't worth his time, not bothering to even consider Dueling him and instead ignored his challenge to Duel. Yūri's interest in Yūgo sparked only after he heard Yūgo had defeated Serena and finally agreed to his challenge as he now considers Yūgo capable of providing more fun to his hunting game. After dueling Yūgo, Yūri acknowledges Yūgo's skill due to how much fun he had when they dueled, stating how Yūgo is not like his previous opponents and he would've Duel Yūgo sooner if he knew it would be so fun, taking back his earlier statement of Yūgo being a nuisance.

After Zarc's defeat, the hostilities between them seemed to have ceased for good and their relationship has improved significantly, particularly Yūgo not showing any kind of hostility against Yūri and the two, together with Yūto, even willingly work together to support Yūya. This may implied that Yūgo has forgiven Yūri.