Could be the translator.I'm still a bit insecure about the child. If remember correctly some chapter called it the son and now it's a daughter... And after reading the other comments it looks like I'm not the only one "confused"...
The author would have also obviously made the child have much shorter hair if it was a boy. You can’t apply western standards to Asian cultures. Very different mindset.Could be the translator.
I don't remember if the translation ever refer to her gender, but in the artist's Twitter, readers usually call the kid as daughter.