The Japanese pension system

Most of all Japanese citizens have to pay the money for the pension. It is our obligation as a Japanese citizen, but we have actually doubled that what we really can receive it when we are retired or have reached a certain age.
Because the pension system has begun to collapse. In fact, pension beneficiaries income(amount) of the pension has gotten lesser and lesser in spite of the increasing the price in addition, our birth rate has kept decreasing.
There is a condition for receiving the pension, which is that we have to pay for more than twenty-five years, otherwise we would lose the right to receive the pension.
Many people can't afford to pay the money for the pension at the moment, but there is a way that we can go back as long as ten years and pay the money for it. It means we can pay the money when we are able to pay it. On one hand it is proven that the Japanese government have enough money for the pension, so they desperately collect the money from its citizens. If my memory is correct, it was just as far back as five years what we could pay when I was young. But Japanese government has extended extra five years so that we can trace ten years for paying.

I'm amazed at your English ability, the things I picked out are words that are difficult for a lot of non-English speakers, but it was all clear enough for me to read, well done!

Japanese Pension System

Most Japanese workers have to pay money(part of their salary) for the pension. It is our obligation as a Japanese citizen, but we actually double what we really can receive when we retire or reach a certain age.
Because the pension system has began to collapse. In fact, pension beneficiaries' income(amount) from the pension has become less and less in spite of the increasing the amount that we pay and our birth rate has kept decreasing.
There is a condition for receiving the pension, which is that we have to pay for more than twenty-five years otherwise we would lose the right to receive the pension.
Many people can't afford to pay the money for the pension at the moment, but there is a way that we can go back as long as ten years and pay the money for it. It means we can pay the money when we can afford to pay it. On the hand, it is proven that the Japanese government does not have enough money for the pension, so they desperately collect the money from its citizens. If my memory is correct, it was just as far back as five years that we can pay when I was young. But Japanese government has extended extra five years, so that we can trace back to ten years for paying.

Very well written! Good job :)