Two things: Personally, I think you have bragging rights if you land, on hook and line, any fish smaller than a 1 yen coin (I keep a 1 yen coin with my tanago-style tackle box). And, while not classic tanago fishing, perhaps dropshot rigging might be worth trying- a split shot at the very end of the line to see if it will drop very quickly past those other species, and present bait at a fixed distance above bottom instead of a float which keeps bait at a fixed distance below the surface.