Small green frogs

I am not good at sepcifying what kind of frog it is. A small green one which is found here and there around our house and farm. In the farm we can find other kinds of frogs as well, they are definately a lot bigger and different color. Probably this small frog try to hide itself from any enemies which would like to eat it! When it is on a green leaf, perhaps hard for enemies to find it though it is not that hard for human beings. Perhaps our eyes can judge a lot more colors.
At the time of transplanting rice pots, they sing a lot one after another. It's a kind of countryside symbol.

Hayaokidori website