@runrin It's weird, but makes sense. Remember the chapter when Ponko jumped off the boat to try and rescue Yuuna? She activated swimming mode, which was her ponytail spinning like a propeller. Wasn't very effective, but the bone explains how it works.
Poor Yuuna, wetting your bed in seventh grade has got be
insanely embarrassing. Hopefully for her Ponko doesn't go tell everyone in town the updated info. (She previously told everyone Yuuna was wetting her bed until fifth grade.)