Ah... Well, it was bound to come up sooner or later.

Akechi gazes off into the distance, one hand on his hip. How to put this...

"I had identified you all, and when I first approached you in the hallway, I already knew you were the Phantom Thieves. However, our conversation the next day genuinely fascinated me. I suppose you could say that I wanted to pick your brain, understand your thought processes and what made you tick..."

Slowly, his focus returns to Ren, and he shakes his head. "But I wouldn't have brought you to Jazz Jin on a whim. I suppose, against my better judgment, I did enjoy our meetings and conversations."

That's a lot of words to express attachment, but in true Akechi fashion, he can't just say he cares. It has to be filtered, implicit.