Besides raising stock prices, the main idea behind QQE with a negative interest rate was to further weaken the Yen. This effect could not be seen since the Introduction of QQE with a negative interest rate. It is assumed that because of the "risk-off mode" of global investors demand for the "safe haven" Yen has increased, leading to an appreciation of the yen.
Main point of QQE with negative interest rate was to raise stock prices. Since the introduction of QQE with negative interest rate this effect could not be seen in Nikkei stock prices.