One of the central themes in "Marvel's Spider-Man: City At War" is the struggle between Peter Parker's civilian life and his responsibilities as Spider-Man. This theme explores the challenges and sacrifices that come with leading a double life, highlighting the internal conflict and the impact on personal relationships.

The book delves into the famous Spider-Man mantra, "With great power comes great responsibility." This theme is evident as Peter Parker navigates his role as a superhero, making tough decisions to protect the city while dealing with the consequences of his actions. It underscores the moral dilemmas and the weight of responsibility that come with his powers.

The relationships between characters such as Mary Jane, Aunt May, and Miles Morales are pivotal in the story. The theme of friendship and loyalty is explored through their interactions and support for Peter Parker. These bonds are tested and strengthened throughout the narrative, showcasing the importance of trust and camaraderie in the face of adversity.