Umehara Masayoshi is the best friend of the protagonist Junichi, whose father runs a sushi restaurant called "Azuma Zushi". There is also a sushi restaurant in Choshi City called "Aduma Zushi". It's just spelled differently by one letter!
This sushi restaurant was founded in 1966 and offers seasonal nigiri sushi, golden eye snapper kamameshi, and datemaki rolls.