Upon first seeing Earth from the Azatos Empire's survey ship, Chief Investigator Liza Luna plans to eradicate every lifeform on it immediately, leaving behind only useful resources. While surveying the planet, Liza discovers that human civilization has evolved at a pathetic rate compared to other lifeforms. Liza makes her way to the surface of the planet to properly inspect and understand its inhabitants. Still convinced that there is nothing beneficial to be found, the investigator makes her way into a cafe to gauge the planet's food culture. Liza walks into a cat cafe, where she meets creatures far cuter than anything else in the galaxy. Motivated by this new discovery, Liza decides to investigate Earth's numerous adorable inhabitants.

While saving a child from harm, otaku Asahi Ikusaba is transported to another world and believes he has reincarnated with cheat skills similar to those of the characters from his favorite games and novels. Unfortunately, reality strikes when an encounter with a powerful monster shows that he is still nothing more than an average person. In this moment of extreme danger, Asahi instinctively calls out to his overly doting sister, Maya, who appears out of nowhere, possessing the overpowered abilities he thought he had. Maya is ecstatic to see her brother again and resolves to use her newfound powers to protect Asahi no matter what. Together, the close-knit siblings attempt to find a way back home while enjoying their new lives. However, it soon becomes clear that their arrival in this world may have had a purpose. With the Demon King's overwhelmingly powerful army approaching, no one but Maya seems to be able to stand in its way.

The movie will focus on Ai Haibara's past and will reconstruct the Mystery Train arc from the television anime, which shows Haibara and Conan meeting for the first time. The movie will also include scenes from the Kurogane no Submarine (Black Iron Submarine) movie.

Far to the north of the world lies Hell's Gate, a portal formerly used by the Demon Lord to invade the human realm. Thanks to the legendary hero Shion Bladearts, wielder of Excalibur, and his loyal band of companions, the Gate was sealed off and the demonic threat was vanquished. Unfortunately, the seal was incomplete and has begun to weaken, allowing the demons to once again begin their attack. Worried about the safety of his village, selfish and perverted farmer Touka Scott dig pitfalls to defend against the demons. But fear not, for Shion is on his way to reseal Hell's Gate and save humanity! Or at least he was, because the legendary hero is dead, having fallen into one of the pitfalls Touka dug. Luckily, dealing with the dead is the specialty of necromancer Anri Haynesworth. While she can't revive him, Anri can at least salvage their quest by forcing Touka's soul into Shion's rotting body and dragging him along to Hell's Gate in Shion's place. Not wanting to be left behind, Touka's childhood friend Yuna Yunis tags along. Together, the three of them set out as what just might be the most unsuitable party to ever try to save the world!