Dennis Macfield/Relationship

Yūri
Yūri appears to be one of Dennis's friends, it is shown that they are on good terms and Yūri seems to trust Dennis to help with his mission asking if he had tracked down Yuzu, Dennis does however seem to be against Yūri's methods as he is seen frowning when Yūri turns Olga and Halil. His trust in Yūri is shown when neither is nor Yuzu are at the ice field so he assumed Yūri took her.

Yūya Sakaki
Yūya and Dennis do seem to have held a friendly relationship as Dennis saved Yūya from Ken and Makoto, Yūya seems to like and respect Dennis, he is also able to trust Dennis as it is shown he trusts Dennis to know about the other dimensions (although Dennis already knew). When Shun revealed Dennis's identity Yūya was shown to be in doubt of him.

Serena
Serena does not seem to like Dennis very much and Dennis does not seem to want to make any kind of relationship with Serena, the only reason Dennis is near Serena is to make sure he can capture her and bring her to the professor. When Shun revealed Dennis's identity all of Serena's trust for him was broken.

Yuzu Hīragi
Not much of Dennis and Yuzu's relationship has been shown, however it seems that his mission is primarily to capture Yuzu, Yuzu meanwhile trusts him. When Shun revealed Dennis's identity Yuzu's trust for him is broken.

Shun Kurosaki
Dennis and Shun haven't interacted much, their first interaction was their duel in the underground arena where Shun began to question if Dennis really was from LDS, in their second Duel Shun wanted to confirm his suspicions, when his suspicions were brought further forwards by the reveal that Dennis had a Fusion card, Dennis Fusion Summoned "Antique Gear Chaos Giant" which confirmed Shuns theory.