Zauo (Jumbo-Tsuribune Tsurikichi) puts a wild spin on the idea of fresh fish - you actually fish for your dinner from tanks built into the restaurant! They've got two spots in Osaka (one near Dotonbori, another in Shin-Sekai), and our family says it's a total blast, especially with kids.
The concept is genius: catch your own fish, then hand it over to the chefs who'll prepare it however you like - sashimi, grilled, tempura, you name it. When someone catches a fish, the staff beats drums and cheers, turning dinner into a celebration. Plus, the boats you sit in while fishing add another layer of fun to the whole experience.
Our family particularly recommends trying for the sea bream - apparently it's one of the easier fish to catch and tastes great prepared any style.