Ryouhei Arisu is a high school student with no ambitions and just wants to escape from what he feels is a meaningless reality. One night when he is with his two friends Daikichi Karube and Chouta Segawa, they see an abnormally large firework shoot into the sky, an event which signals a permanent change in their lives. Blinded by the incredibly bright explosion, the three find themselves transported to what is known as the Borderland. The only inhabitants of this world are participants of a deadly game where specific tasks must be accomplished if they wish to survive. As the three begin playing to determine how they can get back home, Ryouhei finds himself feeling alive for the very first time in his life.

Red is the opening theme for Kagerou Daze: In a Day's performed by GOUACHE. The music video was released on November 3, 2016 on IA Project's official YouTube channel and advertises the film's release at the end. It was also included on the DVD/BD release of Kagerou Daze: In a Day's but lacks the advertisement. The body of the music video is a mash up of the whole franchise, ideally giving the viewer a refresher before the film's release the next day.

“For us,good or bad, true or false, it is meaningless.”When the world around you isn't what it seems, you may be in the midst of a Bug Man; powerful being who can warp the very nature of one's memories. The Memory Collectors are here to bring order... whether we like it or not.

Fifty years ago, horrific creatures dubbed as the "enemies of humanity" suddenly appeared around the world. To combat these threats, teenagers gifted with supernatural abilities called "Talents"—such as pyrokinesis and time travel—hone their powers at an academy on a secluded island. Nanao Nakajima, however, is quite different from the others on the island: he has no Talent. With many "Talented" teenagers around him, Nanao is often a target for bullying, but even so, he still strives to complete his training. Soon after, two transfer students, the mysterious Kyouya Onodera and the mind-reading Nana Hiiragi, join the class. But just as everyone starts blending as comrades-in-arms, mysterious disappearances begin to threaten the class's entire foundation.