Guard sometimes considers it, but he feels that would just be more painful for her. He knows she sometimes stares at Seku.

I think Seku and Guard would want to try to avoid killing demon Ai, but that depends purely on her actual actions.

The only one who would've sympathized with Onee was Shian, and Onee kinda stepped on that and then smashed it when she wasn't being given money. So basically, Onee screwed herself. I think only Sadame would have any sort of idea as to Shiyoko's plight... but most of them would shake her and tell her to stop being crazy.