It remains to be seen if the yen can stay weak if global risk aversion takes hold again. Market players will be wary of the BOJ taking action in that case, but they may conclude that the central bank won't step in until dollar/yen falls into the 116 range, the BOJ can lower interest rates further into negative territory, but the impact could be limited. For example the ECB did deepen negative deposit rates in December but this was considered a disappointment.