Dont just look at the number, look at the size of the market.
PS4 accounts for over 1/3 of all hardware sales in the UK since 2014.
PS4 accounts for about 1/2 of all hardware sales in Germany since 2014.
PS4 accounts for under 1/4 of all hardware sales in Japan since 2014.
PS4 may have sold more in Japan than any individual European country but it represents a much smaller percentage of the overall market.
Which means Sony has more ability to grow in the japanese market than in Germany or UK.