After downloading EP 1 of the drama, it does appear to be a mini circular saw. The grey rectangle in her right hand is the saw shoe, and the black round thing in the same hand is the upper/lower saw guards, and the part extending beyond her left hand is the battery pack. It's shaped differently from other mini circular saws I've seen, with the handle running perpendicular to the blade motor instead of inline, but perhaps the different brands in Japan do it differently.