Akira Nishino made his debut as Japan coach on Wednesday in a 2-0 loss to Ghana.
In steady rain at Nissan Stadium, Thomas Partey gave Ghana a 1-0 lead in the ninth minute with free kick from the top of the area. Emmanuel Boateng doubled the advantage from the penalty spot in the 51st.
Nishino, who will name his World Cup squad on Thursday, brought in substitutes Shinji Kagawa and Shinji Ozaki in the second half when Japan created more chances but was unable to beat Ghana goalkeeper Richard Ofori.
Japan fired Vahid Halilhodzic last month, only two months before the World Cup opens, and replaced him with Nishino.
Japan will play in Group H at the World Cup with Colombia, Poland and Senegal.