Azure Striker Gunvolt: Fleeting Memories (陽炎のメモリア, Kagerou no Memoria) is a side story written by Toshiaki Tai, first appearing in INTI CREATES' YouTube program Interactive Wave. An English translation by Matt Papa is found on their website.
The first part of the story details the "Lifewave," a mysterious energy that allows the existence of adepts. The first part also details the rise of the Adepts and subsequent rise of the Sumeragi Group.
Parts two through five tell a side story about Dr. Kamizono. The parts give backstory to him and his unnamed son and family. The events surrounding the creation of glaives and Azure Strikers is told in detail. The side story ends in the death of Dr. Kamizono and his associates at the hand of an Adept they had been experimenting on, It is explained that Dr. Kamizono's death was kept in secrecy by Sumeragi. These parts serve as a prologue to the main story of Fleeting Memories.
Parts six through twenty are based around the siblings Rei and Miu. Their lives were forever changed by an encounter with an Adept serial killer known as Raptor "The Obliterator of the Innocent," who suddenly kills Rei and Miu's family. The side story also details their encounter with an Adept named Himeshiro "The Guardian Angel." The 1st season of the Side Story ends with Rei talking with Himeshiro about hunting down Raptor.
The side story received an overall positive reception from fans of Gunvolt. Many readers considered the story to be better than that of the Azure Striker Gunvolt game. After widespread support from fans, Matt Papa, the translator of Fleeting Memories, revealed that Toshiaki Tai was developing a "season two" of the side story. The release date for the continuation has yet to be confirmed.