There's a small black dome in the ceiling. Yousuke worked in a department store. He knows the significance. "What about the camera?" he asks.
"False, I've been informed," Naoto says. "Mr. Kuwabara exhibited a certain paranoia. He desired security—but also feared being spied upon. Ultimately, he elected for a facsimile of a camera, to deter potential intruders."
Meaning, of course, that he would've been fully aware how useless it'd be for picking up a murder. And now that he's missing—things don't look good for him, wherever he is now.
Fake security, Yousuke thinks, and can't help drawing parallels.