A young girl named Kanata Sorami joins the army with the hope of learning to become a good bugler. She is assigned to a place called Seize, which is currently holding a festival where people splash each other with water. She is found by her superior, Rio Kazumiya, who gives her a bath and tells her about the legend of the Fire Maiden. While looking at a bell owned by Rio’s father, an owl steals it, forcing Rio to stop Kanata falling off the balcony trying to get it. As Rio participates in the festival, Kanata decides to search for the bell. She finds it hanging off a ledge, but when she goes to get it she falls into the lake, where she sees the golden skeleton of a winged creature. Stranded at the bottom of a canyon, she plays her bugle where she is responded to by Rio on her trumpet. She takes her to the Time Telling Fortress and plays the trumpet as the sun rises, introducing herself as Kanata’s bugling teacher.

During breakfast, Kanata is introduced to the other members of the 1121st Platoon; Felicia Heideman, Noel Kannagi and Kureha Suminoya. Kureha shows some hostility towards Kanata, but she is assigned to show her around the fort. When Kureha takes Kanata to see the tank of the squadron is kept, which is in the process of being repaired, Kureha expresses her depression because the military often ignores the squadron’s existence. Later that night, Noel and Kanata claim they saw a ghost in the barracks, so Kanata and Kureha are sent to investigate. They learn the place used to be a school. Kureha laments that their platoon is in the middle of nowhere and is generally ignored. The two are surprised by an owl, the same one that stole Rio’s bell, but with Kureha’s help they manage to capture it. They decide to keep it and name it Shuko.

Confronted by soldiers from the 9th Division, Aisha suffers serious injury in front of a frightened Noël. Meanwhile, Filicia takes Col. Hopkins hostage and orders his forces to leave the fortress as they barricade themselves inside. Col. Hopkins divulges his intention to use Aisha to instigate war, in addition to revealing his connection with Noël who once worked with him in reconstructing an ancient bioweapons technology that resulted in the deaths of many people. After being locked up in the distillery, he manages to make his escape in secret. While on tower patrol, Kanata hears a faint and distant signal for cease-fire prompting her to tell the others. Naomi with the support of the townspeople try to convince the 9th Division of the signal for cease-fire but are arrested by Col. Hopkins. Out of options and with an injured Aisha in tow, the girls decide to use the restored Takemikazuchi to stop the 9th Division and prevent all-out war between the nations.

When asked by Mishio what her dream is, Kanata is unsure how to answer. Kanata is given a letter sent to Rio from the Roman Emperor, and goes to find Rio so she can sign it. Whilst in town, she runs into Yumina and learns why Mishio asked her. Kanata later learns from Naomi and Maria that Rio might have wondered off somewhere. Kanata later finds Rio at some ruins, who was wondering about the true story behind the Maidens of Fire that Aisha had told them. Rio then explains that outside of Seize, there are a lot of wars going on. Later that night, Rio takes Kanata on a hot air balloon ride, where she tells her her dream of rebuilding the airplane. The next day, as Kanata is picked to play the role of a fire maiden, Kanata decides her dream is to follow Rio on her dream.