It's not the lack of development so early in the series, it was the utter lack of any worthwhile information in this episode. What did we actually learn in this episode that wasn't established in the first:

- Hinata is richer than Yui
- Hayami lives in an abandoned train
- Hinata and Hayami used to be friends

I am generalizing to make my point, as there are refined points introduced in the first that we didn't know about. But a 12 episode series should not be wasting time so soon in a series. We learned absolutely nothing of value in this episode. Usually, episodes with this startling lack of content are loaded to the brim with fanservice, but there was more of that in the first episode.

My two biggest problems are the utter lack of reaction to Takuma's sudden vision, and the way they are bullying Hayami. Hinata of all people seems very obsessed with Takuma's well being, seems to be the "childhood friend that knows everything about the protagonist" type of character, and dotes on him excessively. However, even after all the fufu-ing over him in the first episode (Lead him here, lead him there, call him -sama), she doesn't even remark on such a significant change?! This should be something amazing to her, like Hayami's reaction at the end of the first episode. But even she doesn't even seem to care that he can suddenly see by the beginning of the second episode.

The second is the way they are bullying Hayami. Yes, it is supposed to bother the audience. I also believe they are supposed to be in middle school (if they are in high school, that makes it that much worse). However, they are acting like elementary schoolers. Name calling, throwing toilet water on her, and then going back to name calling are the best they can come up with after beating the shit out of her in the opening scene and at the end of first episode?

Many of us have seen girls completely ruin each other's lives in series like Great Teacher Onizuka without a single punch thrown. Once you cross the line into violence, you can't backslide from there. It makes it look extremely childish. They already beat her up at the end of the first episode. Days later, they call her smelly. You can't take that kind of antagonism seriously anymore.

If you want to keep the audience interested, you do not simply reiterate the mystery again, without any new information. In you want your antagonists to be taken seriously, you have to maintain their level of hostility or resolve whatever issue there was (and thus end their role as the antagonist).