An idea springs to mind, the same one he keeps having and yet is unable to completely dismiss. But to speak of it to someone who isn't part of the Phantom Thieves, especially when he barely knows much about it himself....

If Rubedo can help, then perhaps he should say something. Clearly Yusuke is struggling with it, biting his lip delicately before speaking.

"There is a strange phenomenon present in the world from which Futaba and I originate. It is not something I speak of lightly, but perhaps you can make something of it with the theories you've already crafted. I must swear you to secrecy before I continue."