If the first film's main theme could be summed up as “revenge”, then you can probably say that Godzilla: City on the Edge of Battle is all about “humanity”. Following the successful defeat of Godzilla's offspring and the reveal of the true evolved Godzilla, Haruo is left injured and defeated. He is nursed back to health by a member of the new indigenous population of the Earth, the Houtau, until he's well enough to search for any surviving crew members.

In Godzilla: Planet of the Monsters, the conflict was made oddly personal when Haruo swore revenge on the monster that stole the planet from his people. But this sequel seeks to confront his attitude, making it clear that this obsession with revenge can cause Haruo to lose focus with what really matters. This results in a much more appealing character conflict where the protagonist's motivations are explored further. The Godzilla anime film trilogy, written by Gen Urobuchi, introduced a complex premise involving different alien races, a search for a new home among the stars, famous monsters from the Kaiju universe, and a failed Mechagodzilla project. However, it's only in this film that these concepts are properly explored to add further depth to a story about killing Godzilla.

After meeting the new indigenous people of Earth, the remnants of the Godzilla extermination team reaffirm their goal of taking back the Earth by pursuing a new strategy. This eventually leads them to discover the remains of Mechagodzilla, the robot created by the Bilusaludo people out of a sentient nanometal. The nanometal has spread, forming an entire city with the single-minded goal of destroying not only Godzilla, but anything created from Godzilla's genes. Even though the vast majority of the film from this point on takes place within the safety of Mechagodzilla City, this gives rise to the film's true main conflicts arise. Fans of Gen Urobuchi's dark twists and ideas will find the tension in Godzilla: City on the Edge of Battle very familiar.

Although Haruo has improved as a character and evolved as a personality, it's difficult to say the same for the rest of the cast. In the case of the Bilusaludo, they finally appear to have some sort of purpose in the story, but other individual crew members continue to have few defining qualities. Even Yuko, who received significantly more screen time than in Planet of the Monsters, has little going on outside of her relationship with Haruo. Similarly, the mysterious Metphies from the Exif race doesn't have much to do until he teases the appearance of Ghidorah for the final part of the trilogy, Godzilla: World Eater. Minor characters just play the role of window dressing until a relevant plot arises.

Unfortunately, this does slow the pace of the second act considerably, since the visuals mostly just involve characters wandering around the nanometal city. It drags compared to the first act, which delivers a more intimate exploration of Earth 20,000 years later, where the backgrounds really stand out in a clash between the misty blues of the forest and the bright orange lights within the Houtua's underground dwelling. The use of color in the first act implicitly introduces the Houtua as trustworthy people and their home as a safe haven from the monsters above. However, the time spent in Mechagodzilla city felt more flat. The green lights and cold grays have little contrast with their surroundings, and there are few opportunities to see new parts of the world after the team has decided to hole up there. It's a shame because after background director Yukihiro Shibutani's work on Godzilla: Planet of the Monsters, many fans may be expecting to see more of his depiction of Earth.

However, even though the film is less visually interesting in its second act, the climax sets a new standard for Polygon Pictures. After working on the mechs in two seasons of Knights of Sidonia and the first Godzilla film, their animation has become even more appreciable. Watching the mechs fly about Mechagodzilla city is the highlight of the film overall. The action scenes are few and far between this time, but when the film finally gets to the battle with Godzilla, the advantages of 3D animation are clear in portraying these complex designs. While Godzilla: City on the Edge of Battle avoids including one much-anticipated action confrontation, the film is better for it and manages to make up for the gap with these stunning moments.

Godzilla: City on the Edge of Battle still feels like an incomplete story, but there's a clearer path to the finish line with the reveal of new narrative elements and a redefined goal at the film's end. While it doesn't fix many of the issues from the first film, Haruo's development manages to sell a more character-driven narrative and makes his relationships more empathetic. It's perhaps not the film that fans were expecting, but it's the film this trilogy needed to lead into an epic conclusion in Godzilla: World Eater.