Apparently Mash is best girl since she accurately knows the size of Master's "thing", despite the fact that those three apparently can pop up at any time.
Morning there Mash!Fine weather today!My cover got blown already? As expected of the kouhai!How'd you figure that I was an imposter?Just why do you know the size of this thing?The size of his you-know-what was off? Ahaha, I see!Well, for things I've never seen, all I can do is imagine them you know~