That's because you never had a job that got you on the Kousei Nenkin and you obviously didn't pay into the Kokumin Nenkin very long. That and/or you were on reduced contributions due to having no income because you didn't hit a lick at a snake the whole time you've been here. The averages paid out are 147,000 for the former and 55,000 for the latter. Those figures are per month, not every two months.
It is possible to receive up to a maximum of 65,000 per month on the Kokumin Nenkin and up to a maximum of 100,000 per month on the Kousei Nenkin. So from a theoretical maximum possible of 165,000 per month you're getting about 10% of that....1/4 of the Kokumin and nothing from the Kousei.
One should not use your case as a basis on which to get some idea about Japanese government pension plans.