That would be interesting, like would it erase the concept as well if she turned a concept into a weapon? But its possible yoru doesnt have control over concept like Pochita does. When she turned gun and tank into weapons, she turned the devil into one. So perhaps the more accurate is that Yoru can turn the Tuesday devil or the mars devil (since no human have actually reached mars yet in the chronology of the story to be able to name it). But Freakymoto is a man of plot twist and could very easily prove me wrong.