Justice for Love: End of the World/Development

Early concept
After the 2006 remake of Sinking of Japan recieved criticism for its ridiculous and unrealistic plot, Japanese studio Toho, known for the Godzilla franchise, approached Shusuke Kaneko on producing another science fiction film while the Godzilla franchise was placed on a ten-year hiatus. Kaneko is known for Gamera: Guardian of the Universe, which attracted unprecedented critical acclaim for a kaiju film, and Godzilla, Mothra and King Ghidorah: Giant Monsters All-Out Attack, the 25th installment of the Godzilla franchise. At the time, there was no consensus on what will be the film's main premise, due to the renewed popularity of disaster and sci-fi films, including the upcoming releases of The Day the Earth Stood Still and 2012 in 2008 and 2009, respectively. On February 15, 2013, the Chelyabinsk meteor event took place over Chelyabinsk Oblast in Russia. Due to the incident, interest in asteroid impact events have drawn renewed attention, while the film's concept was then finalized on visualizing the possible effects of a large asteroid impact, a rarity in the disaster film genre, as most films that had previously been released usually end with Earth being saved from the catastrophe. It was decided from the outset that it would be clear from the beginning that the asteroid threat must be depicted as if it were a real event, and to show the entire world would actually end in the film, due to sci-fi films lacking respect from film critics. In order to achieve this, the filmmakers took inspiration and influences from real impact events that took place in Earth's history.

The Cretaceous–Paleogene extinction event served as the main inspiration for the film, which is known for wiping out the non-avian dinosaurs 66 million years ago, following the impact of a 10 to 15 kilometer asteroid in the Gulf of Mexico's Yucatán Peninsula. Other impact events that served inspiration included the 1908 Tunguska event, and the 2013 Chelyabinsk meteor event. Beyond impact events, pseudoscientific concepts were also used as influences for the film, from the Nemesis & Shiva hypothesis, to the Nibiru cataclysm.

Pre-production
Pre-production only began in 2019, as the project went into development hell for several years due to Toho focusing on reviving the Godzilla series, following the release of the 2014 American reboot film by Legendary Pictures. The film became a co-production with Philippine studio GMA Pictures following the success of 2018's The Return of Godzilla, the first Godzilla film that was co-produced by Toho with a Philippine film studio. GMA Pictures has a different concept in mind, however, as they opted to produce a film focusing on relationships instead of a sci-fi disaster film. Both studios later agreed to merge the two concepts into one.

GMA Pictures hired Gina Alajar as the film's director, with the story written by Des Garbes-Severino, Maria Zita S. Garganera, and Suzette Doctolero, while Toho hired Ryuhei Kitamura and Masato Kato to write the film's screenplay. The film's screenplay was adapted from The Last War, replacing the nuclear warfare theme with contemporary concerns regarding astronomical impacts on Earth. Doctolero added elements from the Philippine drama genre, such as adding a depressed woman and her sibling obsessed in seeking revenge into the film. Doctolero was influenced by previous work including Hiram na Anak, Bihag, and especially Rhodora X. Alajar wanted to produce a movie that is character-driven instead of the usual plot-based stories, and as a result, the entire film is shown from only one perspective, while minimizing or completely removing the other perspectives of the film. "I want to make a movie about relationships, probably a family drama or a love story. I love character-driven rather than plot-based stories. Given a choice, I prefer experimental to formulaic movies."

- Gina Alajar, director of #JusticeForLove: End of the World

Casting
Yasmien Kurdi was cast as Alicia Salvacion, a depressed woman that suffered through a series of unfortunate events. The character was written specifically for Kurdi, as Alajar already knew Kurdi's potential as an prominent drama actress, as shown from her previous work in Sa Piling ni Nanay and Hindi Ko Kayang Iwan Ka. Alajar would later praise Kurdi following the film's success, and after both of them were cast in Start-Up PH two years later. Max Collins was cast only due to her birthplace being San Francisco, the film's main setting. Rebecca Rittenhouse was cast as an astronomer, who would discover the asteroid. While all of her scenes were filmed, she does not appear in the finished film, due to the removal of additional perspectives in favor of entirely focusing on Alicia's perspective. As a consequence, the film's intended title, Asteroid Clara, was changed to Justice for Alicia.

The rest of the cast were added later, including Martin del Rosario as Alicia's younger brother, Rose Byrne as an investigator, Ivana Alawi as Mylene's younger sister, Jade Lopez as a reporter, Ysabel Ortega as one of Mylene's friends, Jean Garcia as Alicia's mother, Lovely Rivero as Romina's sister, and Gabriella Wilde as Lori's friend in San Francisco. Additional cast include Empress Schuck, Jay Manalo, Reese Tuazon, Mikael Daez, and Kris Bernal. Some of the cast prepared for their roles in the film, including watching disaster films as reference. For her role in the film, Rittenhouse consulted various astronomers, and also instructed to watch documentaries regarding astronomy and the Cretaceous–Paleogene extinction, as Rittenhouse had no previous experience on sci-fi disaster films.

Filming
Principal photography began on August 2019, and ended in May 2020. The COVID-19 pandemic forced filming to be suspended temporarily. Most of the film was shot in San Francisco, while some scenes were also filmed in Manila and Sacramento. Filming locations in San Francisco included the Embarcadero, Telegraph Hill, North Beach, and Pacific Heights. The Golden Gate Bridge, Highway and Transportation District only allowed filming for one scene on the Golden Gate Bridge, after discovering from the script that the film also contained a destruction scene of the bridge.

For the streetcar accident scene, the filmmakers had to apply several permits from San Francisco Municipal Railway (Muni) to use their F Market streetcar line in the film. A small portion of Market Street had to be closed for several days. The filmmakers initially requested for a PCC streetcar, but Muni refused and decided to use one of their own rolling stock, Car No. 130, which was taken out of service after 2010. Operations on the F Market line was not affected during filming, as service was temporarily suspended from March 2020 to May 2021 due to the pandemic.

Post-production
A destruction scene of Tokyo was later added during post-production, replacing the original scene which takes place in South Africa. The Tokyo Tower prop used in the film was based from the one built for Godzilla: Tokyo S.O.S. 16 years ago. The scene was completely shot in the Toho lot. A majority of the miniatures were built at 1:33 scale while the Tokyo Tower prop is scaled up to 1:20 scale. Unlike the other destruction scenes in the film, which were portrayed by CGI, the destruction of Tokyo was portrayed in the traditional manner, using miniatures that were blown up by real explosives. This was done as a tribute to Toho's previous films that used a similar method.

For the main impact scene in the climax, there is still some debate within the scientific community regarding the firestorm effects during the Cretaceous–Paleogene extinction. The filmmakers discussed ways to combine scientific facts with fictional elements, the latter being for entertainment purposes, for the firestorm sequence. The final result is a compromise; after the asteroid's impact with Earth, it triggered a rapidly expanding wave of intense heat and thick hot smoke that moves faster than the speed of sound, vaporizing anything it touches in its path. It is described by visual effects supervisor Atsuki Sato as a "literal wall of fire".

A miniature scale model of the Empire State Building was also used during the destruction of New York City, but it is not specified in which scale the model was built, but it is presumed to be built in 1:20 scale just like with the Tokyo Tower prop. Additional destruction footage includes Sacramento being engulfed by the firestorm and a destruction scene of Los Angeles by another asteroid fragment exploding in an air burst.

The effects of impact winter is accurately portrayed in the film's climax, but the duration was exaggerated, however, as the scene takes place 30 years after the asteroid's impact, while in reality, the resulting impact winter from the Cretaceous–Paleogene extinction possibly lasted for only a decade.

Los Angeles airburst scene myth
A miniature scale model of Downtown Los Angeles in 1:20 scale was built for the film's airburst scene, the most detailed miniature work Toho had produced for the film, and was identical to the real location. The shockwave was portrayed by blowing compressed air towards the Downtown Los Angeles miniature, based on techniques used in The Last War for its nuclear attack scenes. Short clips from this scene appears in the film's international trailer, but the entire scene does not appear anywhere in the film itself.

The reasons given as to why the airburst scene was removed vary by source. Director Gina Alajar mentioned that the scene was removed due to the film's running time, while screenwriter Ryuhei Kitamura claims that the similarities to the 1908 Tunguska event was the reason why the airburst scene did not make it into the finished film.

A popular myth has persisted that Rebecca Rittenhouse requested the filmmakers to remove the Los Angeles airburst scene, due to Los Angeles being her hometown, but Rittenhouse later denied this in an interview, as all of the visual effects work were done in Toho's studios in Japan, while majority of filming were in California and the Philippines. This is further evidenced by the fact that all of the cast members (including Rittenhouse) were only able to watch the destruction scenes during the film's theatrical release.

Early concept
In an interview with Gabriella Wilde in 2021, it is revealed that there is enough footage for a four-hour version of #JusticeForLove: End of the World, resulting in almost 1 hour and 30 minutes of footage being cut during post-production. A year later, during in an interview for Maggie, Rebecca Rittenhouse mentioned being cast for a "sci-fi disaster film" that ultimately went unused.

On December 24, 2021, Don't Look Up was released on Netflix internationally. Its director, producer, and writer, Adam McKay, was certainly aware of the production of #JusticeForLove: End of the World, and influenced him to include a character based on Rittenhouse's cut character into his own film, with Jennifer Lawrence being cast for the role. McKay wrote the character specifically for Lawrence.

On April 2024, Roland Emmerich was announced as the director for an upcoming American remake of #JusticeForLove: End of the World, with a planned 2026 release. In an attempt to renew attention on the original film, and as a response to the issues mentioned by both Wilde and Rittenhouse, Japanese studio Toho decided to release a revised version of the film, to be released jointly alongside the upcoming American remake.

Post-production
"We weren't interested on releasing a completely different movie. We only wanted the movie to follow what we envisioned originally. [Rebecca] Rittenhouse prepared a lot for her role, only to be omitted by the director [Gina Alajar]. That's why we did what we did. We didn't really change the story. We just gave it an additional perspective. We gave Rittenhouse the recognition that she deserved."

- Ryuhei Kitamura on the film's alterations

In the revised version, the film's story now focuses on Rittenhouse's character, while Mylene and Alicia's story was minimized by removing several important scenes and characters, including removing the streetcar accident scene, and removing Ethan's revenge subplot completely. Scenes featuring Cristina Alvarez and Mylene's family were also removed.

Footage from the 2022 short film The Final Moments by GMA Pictures was also used for Alicia and Corazon's death scene, the destruction of Manila, and the rest of the Philippine archipelago.