The restaurant, hnh? Perhaps their escape artist thought he'd have an easier time of it going out through the front. Zoro knew none of this was what the pup thought he wanted. He knew Noctis had come to define himself as a thief on the run. But the truth was, Noctis wasn't free anymore, and not just because he'd been purchased at auction. The authorities knew who he was now, and none too fondly. If they saw evidence that he couldn't be tamed as a Slave, they'd put him down.
Noctis obviously didn't like him. But Zoro figured he'd still probably prefer working in a restaurant for him and Sanji to being dead.
Zoro hung back at the end of the hall, watching where he could just see Noctis at the locked door to the stairs. Oni Giri looked a bit rustic, as most traditionally-influenced Japanese restaurants did. But they had modern thumb locks on the doors, and it hadn't been coded to accept Noctis yet. What was he going to do with that?