The Shopkeeper runs Itan's Ramen Darou and does the cooking himself. He's known for being almost impossibly quiet—so quiet, actually, that he's terrible at talking to people. This shared inability to communicate has created an unexpected bond between him and Shouko Komi; they can have whole conversations without saying a word, much like Komi does with her own family.
The ramen shop operates under five Golden Rules that are basically non-negotiable:
1. Don't speak.
2. Buy your ticket and sit down immediately.
3. Be polite, show respect to the shopkeeper, and wait calmly.
4. Leave your phone alone.
5. Return your bowl the second you're done and give up your seat.
Komi takes to these rules naturally. Since she already shares the Shopkeeper's communication struggles, she has no trouble following his system and is basically the ideal customer in his eyes.
He first appears in episode 5 of the anime and chapter 65 of the manga.
Content compiled by AnimeList.moe from publicly available sources.