This almost felt like a chapter from another story, and not just because I forgot what happened in the first one. Even after reading the left turn felt somewhat jarring. Talk about Drama with a capital D.
I know! I had to re-read the first chapter to remember what was happening and where we were. It does pretty much continue directly from the end of that chapter, though. It's just that the beginning of the first chapter is so different.
As for whether it is incest (not that it matters, it is a story folks, and an extremely far fetched science fantasy one at that) I am thinking it probably TECHNICALLY isn't. If you recall, the last thing Minami's 'mother' said to her was, "I'm not your mother!" In addition, Minami is obviously some sort of experimental subject herself, with her ultra high bone density and extreme speed, endurance, and strength. I mean, she was hit by a car and got up and ran home! Normal people don't do that! So I'd guess she and her 'mother' were both experimental subjects and for some reason her mother became unstable and ran off with her or something and the other girl is her clone.