Actually, having just found a torrent feed for this one, I'll chime in.
Mercury's first transformation, in episode 2, was fairly clearly damn-near-instant. She's falling from a third-story balcony, and is transformed in time to make a soft landing on her feet. Three-story fall is what, a couple of seconds at most?
Mercury's first transformation, in episode 2, was fairly clearly damn-near-instant. She's falling from a third-story balcony, and is transformed in time to make a soft landing on her feet. Three-story fall is what, a couple of seconds at most?