Yes Nintendo owns Japan now.
Xbox has never been a presence and Playstation has been in decline ever since the PS2 era ended. The Japanese just haven't really cared much for Playstation consoles after PS2.
Japan prefers handhelds which gives Switch a huge advantage. But also most of the mega selling series in Japan are Nintendo titles. The only mega series that isn't Nintendo is Monster Hunter but versions of that series are now also coming on Nintendo, and FF and DQ are still big sellers but DQ is also now on Nintendo and Nintendo is also getting plenty of FF stuff even if it isn't getting the brand new mainline FF series.
Basically Playstation is a side system in Japan now. From a hardware and software perspective what Japan wants is almost entirely on Nintendo alone.