Ninjas, of course! They would come to relax after a long day of training or missions. Also, fans of the ninja world from within the story would be there. Maybe even some of the village leaders would stop by to show support for the local business.
Some of the older villagers who have watched Naruto grow up would be regulars. They would come to support his business and also to reminisce about the old days. And don't forget the jonin who are always on the lookout for a good meal. They would appreciate Naruto's hard work and the unique atmosphere of his restaurant.
Other ninjas would be likely customers. They need things like kunai, shuriken, and ninja wire which Naruto could sell in his store.
Mostly wizards and witches, of course. They would be the main clientele as they are the ones who can fully appreciate the magical elements of the restaurant. Students from Hogwarts during Hogsmeade weekends or holidays would also flock there.
His friends from the village could be his customers. They might need seals for their various missions or personal use.
You can offer special promotions and discounts. That often attracts more people to your restaurant.
I think magical creatures would also be customers. Maybe house - elves would be sent to pick up treats for their wizarding families. Hippogriffs might be lured by some special bird - shaped pastries. And even centaurs, if they were feeling a bit more adventurous, could come to the edge of the Forbidden Forest where the bakery might be located to get some goodies.
Her old Hogwarts friends would be very likely customers. They would come to support her new business and also to relive their old memories together. Hermione would probably come often to discuss books and new spells while having a drink.
The 'Friend Code Restaurant Story' restaurant can attract customers by creating a sense of exclusivity. For example, if only those with friend codes can access certain menu items or events. Also, word - of - mouth will spread as friends share their codes with each other, bringing in new customers.
His ninja friends like Sasuke, Sakura, and Kakashi would surely be regulars. Sasuke might come to buy things secretly to support Naruto's business. Sakura could be there to get supplies for her medical ninja work if it's a general store. And Kakashi would stop by for a chat and to pick up some new reading material if Naruto sold books.
His old ninja friends like Sasuke, Sakura could be regulars.