Was wondering how crab soup is related to guns, turns out it's about how trying to get the meat out of crab legs looks like cleaning the gun's barrel. Well, at least that's what i managed to look up, keywords to google - "Hokkaido crab teppo gun soup", if you are interested.
A bit confused about Kyu-chan getting embarrassed over saying "mom". Was it some Japanese word only kids would usually use to call their mothers?