Scotland beat a weakened and undisciplined Japan 26-13 on Saturday in the first of two rugby tests.
Shota Horie scored the opening try for Japan but Scotland fought back through a penalty try in the first half and another try by Willem Nel just after the break that gave the visitors a 23-10 lead.
Japan conceded 11 penalties in the first half, including two yellow cards. Hendrik Tui and Rikiya Matsuda were sent off.
Japan was ahead 10-9 when Matsuda was penalized for a deliberate knockdown which led to Scotland receiving a penalty try and taking a 16-10 lead at halftime.
Japan was unable to defend with only 13 players on the field as Nel crashed over for the five-pointer from close range.
Japan pressed hard and dominated the closing minutes but was unable to hold onto the ball at crucial times as the Scots defended well.
Scotland beat Japan 45-10 at last year's Rugby World Cup in Japan's only loss of the tournament. Japan was without many of the players from that squad, including captain Michael Leitch, Luke Thompson and Justin Ives.
The two teams play again in Tokyo on June 25.