Sony’s PlayStation 4 has finally debuted in Japan… and it is a big problem for Nintendo. According to Famitsu, the PS4 had a pretty great launch week, moving 322,000 units in its home market debut. The Sony box has clearly accelerated the steady erosion of Nintendo’s 3DS portable console sales. In the week ending February 23rd, the 3DS moved just 30,000 units, down from 41,000 the previous week and 74,000 from a year ago.This drop has been more dramatic than expected since the expensive and stationary PS4 does not really compete for the same audience as the cheap and portable 3DS. Nintendo had prepared for the PS4 arrival by launching a new Dragon Quest Monsters title for 3DS a while ago