Operating loss can be carried forward for next nine years, if a company is eligible for blue tax form (aoiro shinkoku). Nine years. it is a long time. But it will be expired after that.
In the next nine years, a company can use it to offset against taxable profit partially or in full depending on the size of the company. For SMEs, whose capital is less than 100 million yen or paid-in capital of its parent company is less than 500 million yen, the carried loss is fully deductible.
If a company is not regarded as an SME, it is only 65% of its taxable income is ok to offset for a fiscal year starting between April 1 2015 and March 31, 2017. It will be only deductible by 50% for a fiscal year that starts from April 1, 2017.
You can carry the operating loss even if you lose the status for blue (tax) form, but operating loss incurred during the years after you lose the status will not be carried forward.