Japan’s government spends more money that it earns in taxes and duties. It thus has to borrow huge quantities of cash to fund its operations.
The total debt of Japan’s national government is $8,362 Billion.
Now Japan’s annual GDP is $4,602 Billion.
Thus the Debt to GDP ratio:
$8,362 Billion / $4,602 Billion = 181%.
This is not sustainable for the long term.