What kushikatsu is
Kushikatsu is bite-sized meat, seafood and vegetables, skewered and deep-fried in a light breadcrumb coating, served a few skewers at a time so each batch arrives hot. Shinsekai, the retro district built up around Tsutenkaku Tower, is considered the dish's spiritual home in Osaka, and its narrow lantern-lit alleys are dense with kushikatsu counters.
The no-double-dipping rule
Most kushikatsu counters serve a single communal pot of thick, dark dipping sauce shared by everyone at the bar, and the house rule — posted on the wall at the more traditional spots — is one dip only per skewer, since a second dip after a bite means it's touched your mouth. Cabbage leaves are usually provided free at the counter specifically for scooping extra sauce onto an already-bitten skewer without breaking the rule.
How to order
Many counters run an omakase-style set where skewers arrive in a chef's chosen order rather than a full menu you select from up front, which suits the standing-and-eating pace of the format. It's a good dish to order without much Japanese — pointing at what's already skewered and cooking behind the counter works fine.
The rule is taken seriously enough that regulars will genuinely say something if a newcomer double-dips — it's not just a menu footnote, it's real counter etiquette.