Taiyaki: the fish shape
Taiyaki takes its name from its distinctive fish-shaped mould, traditionally filled with sweet red bean paste (anko), though custard, chocolate and seasonal fruit fillings are all common at modern stalls. The shape is purely decorative — a marketing device from the snack's origins — but it's become inseparable from the food itself.
Imagawayaki: the round version
Imagawayaki (known by various regional names elsewhere in Japan) is essentially the same concept in a round, disc-shaped mould rather than a fish — a thicker, cake-like batter shell around a similar range of sweet fillings. It's slightly heartier and often sold in pairs or small stacks rather than individually.
Where to find them
Both are street-stall staples around Osaka's covered shopping arcades and festival stalls, sold fresh and hot rather than pre-made — worth buying from a stall with a visible queue or a mould actively cooking rather than a pre-wrapped display case. Tenjinbashisuji and Dotonbori's side streets are both reliable places to find one.
A companion to Osaka's other sweets
If you've already tried the city's wagashi and fruit sando, taiyaki and imagawayaki round out the street-snack side of Osaka's sweet food culture — cheaper, faster, and eaten walking rather than seated.