Responses
Yeah, I also think that the treasure is related to Emilia (in case she herself isn't the treasure) but I actually don't think the blonde knows what the treasure is, there is no way Ophelia shared the whole info with him because she distrusts anyone besides Emilia so in my opinion Blonde only knows some clues that he doesn't understand but Emilia surely will. That's why he is egging Emilia on. The story will most probably take a fantastical true what with the constant mentions of the goddess.
she's obviously the treasure? and I hope she realizes it and her value soon. Ophelia really didn't see to care for anything else, and would explain his smirk and enjoying the situation with some sillyness to it. I'm sure there's something in the letter regarding it (have not read spoilers, just imo) I think through that last conversation with Ophelia when she gave him the letter, he realized the person he actually couldn't stop looking for or thinking of was Emilia. Especially after realizing Ophelia was only who she was because of being around Emilia. She called him an idiot but will give him a chance because she believes he's capable of realizing and taking action/help her. The other two being unreliable in that regard unable to trust doing the right thing by Emilia without her around.