This mangaka either doesn't know how, or want to draw anything else besides very slim and flat butts, also hip width is small as well. In general female hips should be as wide as shoulders, if not sometimes wider. Thus the first page with female characters in bikinis is totes hilarious 😂 Poor Kayo.
Well I don't read this for the art, as some other reader mentioned, I'm here for the story and the crazy antics of Hibiki.