I've told Belph-san, Varian-san, Veronica-san and Eichi. I suspect Hikage-san knows as well.

[and soon Nico but that PC is still going]

All of them but Veronica-san and Hikage-san know about the happy ending requirements. Again, I first received the information about how to end this game in a preferable manner from Varian-san and Belph-san.