Okay, this is the volume I actually *like* Mitsuru. A lot of what I initially didn't like about her personality is explained when we get to see her family. She really is the MVP of this volume with respect to Kokoro's situation.
Also, if Volume 3 didn't already tip you off, this series is getting dark. Kokoro is starting to crumble under the reality of her situation, and we get to see more about Mr. Asahina and his various unresolved traumas. Volume 4 continues this but pulls back a bit more (no on-screen vomiting, if that's a trigger for you). However, the "true version" of one of Kokoro's yuri daydreams is the darkest story yet, like surprisingly dark. To be fair, this is exactly the kind of dark, twisted story that I absolutely ADORE in horror, so I was shocked and delighted to read it, although the fact that such a story can now be found in Yuri Espoir means that the author is not afraid to have a dark ending for poor Kokoro.
Can't wait to read the next volume!