I can see it in an AU, anything is possible in AUs! but in canon? No. Hanako never hid that he doesn't care about Aoi: He haven't show any interest in her as a person in the intire manga, dismissing her even when she is in danger.
The only times he focus on Aoi have been to use her: He treat her as a convenient tool, with no regard for her comfort or safety. Someone to use to make Akane reveal his status as a clock keeper. Someone to use to expand Nene's lifespam.
When she sees her during the sacrifice arc he is imediately suspicious of her: Is not that he noticed that she was acting 'unlike herself'.
Is that unlike Nene or Akane he does not care about the recently kidnapped girl well being.
So her freedom is not a relief, is merely 'unlikely to a suspicious degree that this girl won agaist No.6', . He may have kept his knife behind his back, hiding any violence for Nene's sake, but the knife is there, he is ready to treat her as any other other nameless danger.
Of course he saw an oportunity and sacrificed Aoi to save Nene, that's the only instances he give Aoi any attention, when she can be of use. A chat on the train means nothing if one minute after it, he will go out of his way to keep her dead.
This consistency just make me belief in this:
Much more than this friendly approach when she decides to get in the train:
It makes me very sad that he is the one she was honest with, since he doesn't care about her feelings and I doubt anything changed here.
Hanako only warned her about her soul being destroyed and invited her to sit with her because he doesn't have anyone else in the train, he is alone. He was written to parallel of Aoi to some extend, and despite isolating himself by his own choice, Hanako doesn't like being alone either.