18 years ago, a strange, celestial body crashed just on the outskirts of Canterlot. A mysterious box was found and studied in the Canterlot Research Facility. Despite the time and effort, its secrets have yet to be unearthed....until now.

6 months had passed since the disappearance of Micro Chips' brother, Gizmo. But upon a mysterious delivery, he and his friends Flash and Sandalwood work to crack the mystery surrounding the incident.

Now, rampaging monsters run amok in Canterlot City, emitting a strange gas that turns others into the same creatures. What's worse, Equestrian Magic seems to have no effect. Fortunately, Gizmo had left something behind. A particular system needed to combat these creatures and uncover the truth.

Flash Sentry now takes up the mantle, to build the winning formula.

In collaboration with Banshee531

Kamen Rider Build Crossover.

Edit 6/24/2020: This story had been featured. I am surprised and grateful. I didn't expect it to happen.