... and, just as Ren knew he would, Akechi spins in his seat, perfectly trusting, the awkward conversation slipping from his mind. "What?"

There's nothing there, of course. But he's still curious, sometimes; still the investigator. He gets up from his seat, and goes to the door to look outside.

When he sees nothing, he opens the Leblanc door, with a chime of the bell, and steps outside. He's left his case; he'll be back.