Sake, and Osaka's neighbours
Osaka itself isn't the region most associated with sake brewing — that reputation belongs more to nearby Kyoto's Fushimi district and Kobe's Nada district, both a short train ride away and worth a dedicated stop if sake is a real interest. Within Osaka, izakaya menus still carry a solid range of sake by the glass or flask, usually with staff willing to point toward something food-friendly if you ask.
The highball's outsized popularity
The whisky highball — whisky, soda and ice, poured long — is one of the most commonly ordered drinks in any Osaka izakaya, a genuinely everyday order rather than a novelty, and it's closely tied to Suntory, the company most responsible for popularising both whisky and the highball format in Japan.
The Yamazaki Distillery
Suntory's Yamazaki Distillery, in Shimamoto just outside Osaka, was founded in 1923 and is Japan's oldest whisky distillery, producing the internationally acclaimed Yamazaki single malt. Tours and tastings are available, generally by reservation, and it's a realistic half-day trip from central Osaka for anyone with an interest in whisky's history in Japan.