I did not imagine that Xbox is horribly unpopular in Japan.
Nikkei Sangyo Shimbun newspaper reported the market share of home-use game machines in 2013 financial year. According to it, the market share of Microsoft was 0.2%. Nintendo was the top-seller, and their market share was 65.1%. Sony (PlayStation) was the second (34.7%).
Figure : Home-use Game Machine Market Share in Japan, 2013
Source is Nikkei Sangyo Shimbun newspaper, the article on 2014 July 28th, and Fami-Tsu (ファミ通).