Isohara may be skinny, but not unflatteringly so. And she avoids one of the trappings of really thin women by actually having some noticeable and bouncy volume to her boobs and butt.
Like...I'm kinda gonna be for real: Isohara has a body type I really love. Probably more so than Shiina (and yes I'm aware how heretical that is to say given what this manga is about. Shiina is still very sexy herself though).
Thank you for the translation.