This kakari-geiko youtube video is an example of how Japanese high school students train. The kakari-geiko looks like that they have some kinds of patterns but it is completely controlled by motodachi (their teacher).
In kakari-geiko, as soon as we see an opening, we should strike that target. We just keep going until motodachi stops us or we hear “Yame (stop)” We have to throw ourselves at our motodachi. We just have to be a striking machine.
Why do we do that?
Simply we are training physical aspect of our kendo and push ourselves to our physical limitation so we can train the mental side of our kendo.
And… by kakari-geiko training,
we will be able to execute strikes without thinking when to strike. When you see an opening, your body will already moving to strike that opening.
As you can see in the video, the students gave what they had from the beginning. They did not try to save their energy to last their kakari-geiko. This is also very important. You have to become tired and hit your physical limitation quickly.
And the other students are cheering the student in kakari-geiko. They are encouraging their kendo mates. It is also important, especially to build team work.