Oh nooo she doesn't look happy!
This chapter makes me worry, not because of anything happening in the story, I think they'll work it out, but because I think this means we'll be finishing this story soon. This feels like a point of no return.
Unless this goes on after they start dating! :o I like when stories do that.
I don’t think this means we are really close to the end of the story. If Sumiko’s interview is any indication, their intention is to build their relationship (be it romantic or friendship) past the misunderstanding.
The author said that instead of being a work that could be classified as Yuri, the story is about the relationship between women (which can, indeed, mean friendship; please let’s not come back to the yuri or yurin’t debate). If their intention was not to make the girls build their relationship past the misunderstanding, they would have said something. And even if people might think (oh we’ll get like 5 chapters of them making up), I don’t believe the author is someone who would do a half-assed job with showing that the characters managed to build a genuine relationship. So I am guessing the 18th chapter marks the end of the first half of the story (in other words, I’d give it ~36 chapters for the story to complete itself, which I think is good enough for a twitter short).
If it’s a story about their relationship, it only makes sense there will be some twists and turns before we get an ending.
Something like:
Aya will feel weird, we will get some introspection from her, Mitsuki will pick up, somehow she will notice Aya found out and finally feel really guilty about it, then they will make up (probably this scene will happen, but before this we will get some more chapters with Mitsuki coming up with a way to say sorry), after making up they will have a heart to heart and then we will get them trying to work out their relationship and try to come to an agreement about what it is.