In order for the model to work, human capital invested by young workers in their firm needs to yield future dividends by contributing to corporate growth; to this end, sustainable growth in corporate sales is necessary. In reality, however, due to prolonged deflation, many firms were forced to lower their growth expectations and were less likely to see sustainable growth in their sales.
As a result, it has become difficult to maintain the mentioned model, and firms seemed to have actively reduced their labor costs by, for example, increasing the number of non-regular employees and rehiring retirees at low wages relative to their labor productivity. I believe that in this way Japanese-style employment practices hit turbulence.