Can I drive as a Student/learner driver?

Hi,
I obtained a Japanese car license but am trying to get
an oogata (unrestricted) motorbike license.

I have had the motorbike riding exam 4 times and have failed(!)
for the simple reason that the slightest mistake you make results
in failure. (The system here claims using a point-system but I`ve
never been told my points)

So that aside, I stopped going to a driving school to practice
as it`s really expensive at 5,000Yen.hour. Now my question:

In my country, its possible to drive on public roads as a ''Learner''
driver provided you have a permit and a ''L'' (for Learner) sign
of certain dimensions and color displayed at the front and back your vehicle.
With this, one can practice driving all they want without having to go to a driving school.Do they have such a concept in Japan? I`m asking because at the licensing centre today, I saw a car with a similar sign (but instead of an ''L'', something was written and one of the kanjis was Šw and ‰^“]). This car did *not* belong to the
licensing centre but was parked in the public car park. Because my japanese language
is limited, I could not ask. Does anyone know about this?

If such a provision exists, I`m thinking I`ll buy a motorbike (I intend to get one anyway) and pratice with it and then go for my driving test.

With automobiles, when you attend a driving school, first you start off practicing to drive the school vehicle within the school premises (where they have a short course) with the instructor sitting next to you (with an extra brake pedal on his side too). When you complete the initial hours (I forgot exactly how many) and reach a certain skill level, you will be allowed to go out onto the public road with the school vehicle, again with the instructor next to you and that extra brake pedal on his side as well. That's how people practice driving an auto here. And I belive those cars have that "school" or "on practice" sign on it.

But you can't be riding with the instructor on a motorcycle, right? You need a license "before" you can drive on public roads at all.

"With automobiles, when you attend a driving school, first you start off practicing to drive the school vehicle within the school premises (where they have a short course) with the instructor sitting next to you (with an extra brake pedal on his side too). When you complete the initial hours (I forgot exactly how many) and reach a certain skill level, you will be allowed to go out onto the public road with the school vehicle, again with the instructor next to you and that extra brake pedal on his side as well. That's how people practice driving an auto here. And I believe those cars have that "school" or "on practice" sign on it."

it is the same in many countries..some countries require that a student with a new license only drive with an experience driver along side for so many hours...