ROFLMAO, this is where the NTR starts. I would actually find it hilarious if the author actually decided to take that turn.
Anyways, what the actual hell happened with Izuki where she talks about turning into a girl? I thought it was a case of gender dysphoria or something similar, where she grew up thinking that she was a boy but, biologically, she had always been female. But she talks about how she turned into a girl? That's some weird phrasing to just gloss over.
TL;DR only NTR can save this series now.