Osaka is the city where a research stipend goes furthest and disappears fastest, and the difference between those two outcomes is entirely a matter of where you eat standing up.
Day one
Land, drop your bag, and go straight to a kaiten-zushi counter for lunch. Not the famous one: the one nearest wherever you are staying, which will be better and half the price. Spend the afternoon in Shinsekai, which is louder and less curated than Dotonbori and where kushikatsu runs about a hundred and thirty yen a skewer. The rule about not double-dipping the sauce is real and enforced socially.
Day two
Nakazakichō in the morning for the coffee shops in converted row houses, then the Umeda Sky Building only if the weather is clear. Evening in a standing bar in Tenma, where the entire district is walkable and nothing has a cover charge. This is the night you will spend the least and remember the most.
Day three
The splurge. One kappo counter, one seating, roughly eight thousand yen, booked before you fly. It is the only reservation on this itinerary and the only thing here that requires planning. Everything else Osaka will hand you if you show up hungry at the right hour.