RE: Everyone's immediate concern
It's important to realise that with Japanese social culture, going on "A date" isn't necessarily romantic; you should have read more than enough series by now where the trope is a misunderstanding over exactly that.
I feel like Rio saw that her assumptions, and that his feelings were that he wanted to bind her or keep her, were wrong and wanted to give back some semblance of "Normal" for Kaede. A nice memory perhaps, probably going to have some chats and experience a "normal" date, not particularly sexual or romantic, but just shopping and a cafe.
Seto on top of this is more...sheepishly embarrassed to tell her about his feelings, rather than distraught? Signs are positive, folks, put hold on doom mongering.