And the end of this chapter marks about 2/3rds of the way through Episode 4 of the anime (specifically timestamp 16:40 of the episode is the conclusion of Manga Ch.12). It managed to bring over a decent amount of the conversations from this sequence, but it still was a bit lackluster compared to what the Manga is showing, gotta admit. It still did a great job of making me interested in these characters enough to look up this manga, though I'm sad it's probably only as far as maybe Episode 7 or so, right now. But the quality is sure worth it.
I assume the next chapter got adapted into the final leg of Episode 4, but I won't know until I read it, which I will do... now...
Edit: Whelp... looks like that's wrong. They adapted a later chapter into the final segment of Episode 4, specifically Chapter 17, when Mahiru gets sick and ends up spending a few days recovering in Amane's bed while he sleeps on the couch. The episode ends near the end of the third part of the chapter in the manga. After that, it jumps back to cover the next few chapters, pretty sure, with Episode 5.
To be honest, it isn't a terrible one to shift. Likely, they wanted as much of the New Year's arc in Episode 5, and that seemed to be the first mostly stand-alone chapter after said arc.