Blue Reflection Sun is a mobile RPG in the Blue Reflection series. It was announced alongside the 2021 sequel Blue Reflection: Second Light and the anime series Blue Reflection Ray.

Wind blowing from South-West before noon, sunny with some clouds. There may not be a lot of clouds, but depending on the region, many Ashfall may be expected". On that day, ever so suddenly, the Ash started falling upon this world. A world trapped in Ash. It is a story of living fleetingly and strongly in such world of the girls who fight against "calamity". ...In the world of gray, only these days were beautiful- "......however, centered at Unatecho of Izumo City and its surrounding region Large scale Ashfall are expected after sunset" It all began a year and a half ago. The day that “Ash” suddenly began to rain on the world. Just another natural phenomenon. Or so we thought. We eventually learned that the Ash is “a toxic substance that invades the body.”