Just to throw this out there, there's something I don't think has been talked about when it comes to Io's recent events.
It wasn't necessarily about
her. By that, I mean it was about
Uta:
Io looks up to Uta, and believes she would actually be dead if she never met her:
So, it seems like Io was trying to protect Uta from Sensei, by becoming Sensei's tool, after finding out that he's holding on to a wizard pic of Uta.
In other words: Io was trying to keep him from fucking up Uta, by offering herself.
It's all she had to offer:
The "parenting" stuff just forced her to stop being in denial about him. He reminded her of her mother. Then
he could even use the same words
she did:
In another timeline, this may have ended on a happy note:
But, even leaving may lead to problems. Albeit, I suppose we'll see.