Ren does try not to laugh at Akechi’s reaction - tries, but fails. The most he’s able to do is restrain a quiet chuckle behind his fist.

“You should’ve seen your face just now.”

If Yusuke were here, he likely would’ve said something about wishing to “capture such a priceless moment in the experience of the human heart,” or another such Yusuke-ism. Ren isn’t Yusuke though, and he doesn’t wish to poke at any of Akechi’s potential sore spots, so he quickly changes the subject back to his suggestion.

“Hm. Could be fun to try out anyway.” Ren shrugs. “And you know this place better than me.”