Kai said he was concerned not only about customers tying up valuable seating space during peak hours, but about the way thin Hakata ramen noodles stretch out and are ruined after too many minutes in the soup.
The restaurant owner first pitched the idea of a smartphone ban on Twitter, and positive responses led to his enacting the policy.
Kai said he is not posting any signs about the phone ban, but he has started speaking to customers individually about keeping their phones put away during mealtime.
"I feel it's entertainment that is bound to include rules," Kai told CNN. "It's like, 'When in Rome, do as the Romans do.' Ramen is a form of entertainment."