Kaito Yashio and his friend Akiho Senomiya are the remaining members of their school's Robotics Club. After Akiho hands in a budget request to the staff room, both she and Kaito, who spends his time playing games on his PokeCon device, visit an old hangar containing a large robot the Robotics Club has been working on since its foundation, Gunvarrel, based on a popular robot anime whose final episode was never aired. The next day, the vice-principal agrees to give the Robotics Club their proposed budget on the condition that they win a robot tournament taking place in two week's time, with the club to be disbanded should they lose. As Kaito and Akiho contemplate if they can pull off such a feat, a mysterious girl is seen making a report.

Kaito and Akiho go with their teacher, Mitsuhiko Nagafukada, to where the Robo-One tournament is being held, though they have no hotel to check into. As Kaito practises with the robot, he experiences a strange sensation for a brief moment. The tournament soon begins and Kaito manages to use his tactics to get through the preliminaries and into the finals. Before the final match, Akiho starts to grow concerned about Kaito, who hadn't gotten a lot of sleep prior to the tournament. The final match soon begins against the reigning champion, Mr. Pleiades, whose robot has some fierce tricks up its sleeve. While Kaito's robot is at a disadvantage against Subaru's, Kaito suddenly experiences an inverse of the ailment Akiho has, slowing down time for him, and makes a counterattack, knocking both of them out, though this technically results in Kaito's loss. Upon returning home, Kaito has a brief encounter with Kill Ballad's creator, Frau Koujirou.

As solar flares start affecting computers, people besides Kaito and his group become able to see Airi, who has begun acting weird lately. A planned maintenance on the Iro-O system that could potentially erase Airi means that Kaito needs to fulfill the conditions for the sixth report before Christmas Eve. After Kaito unlocks the sixth report, Airi states that she wants to go to Kimijima's house for her birthday on Christmas Eve. There, Kaito discovers a machine in his basement containing Airi's original human body. Airi explains how she was cursed with an incurable affliction and always spent her days bedridden, hoping for a White Christmas. She soon met Kimijima, who let her see the world through the Iro-O system. As Airi's condition worsened, Kimijima put Airi into a deep sleep in order to wait for a cure and created the program Airi to keep her company.