Is it mandatory for Korean manhwa boasting their superiority when there's Japanese stuff (a high quality sushi restaurant is not rare in Japan) is it hurt their tiny dick's pride to not competing anything with Japan?
It's very common, but in this series they haven't really overplayed it compared to what you see in other series where the Japanese are always foreign conniving invaders committing underhanded schemes to prevent the poor Koreans from reaching their true potential.
Here, the MC was a chef trained in a Japanese restaurant in Korea, and he's only boasting of better skills than a chef
in this world who would be considered talented
in this world's Japan.
It wouldn't be unreasonable to think that a world under recent threat of demons and an apparently totalitarian government (tho his daughter is chill ig lol) could have progressed differently in its cuisine.