Koto become more and more suspicious as the story go on. Looking back on the first chapter, i didn't think much back then, but now i think she changed attitude quite fast when she learned that he was Miya father, going from talking like she was talking to an acquaintance to pretty much try to seduce him. Since then while it seem like she's trying to support him, it also seem like she's trying to put distance between him and Miya. If what i suspect is true than i think her trying to put distance between them is quite likely since she might hope to hurt Miya even more and the father while she's at it.
Chapter 1 was bad, chapter 2 was great, chapter was 3 was ok, chapter 4 was awesome and now chapter 5 is ok at best .