"It hurts when I move my leg and it's pretty tough," Nakamura said after arriving at Narita airport, referring to a sprained right ankle he sustained in the Scottish Cup final against Dunfermline on Saturday.
Celtic defeated Dunfermline 1-0 in Saturday's Scottish Cup final to complete a league and cup double.
Nakamura earned both the Scottish Player of the Year and Scottish Football Writers' Player of the Year awards for his outstanding performance throughout the season.
Japan faces Montenegro in Shizuoka on Friday and then take on Colombia on June 5 in Saitama in its final warm-up for the defense of the Asian Cup in July.
Ivica Osim's team has been drawn against 2006 Asian Games gold medalists Qatar, the United Arab Emirates and Vietnam.
Brenton Tarrant, the shooter from New Zealand's Christchurch, was not a lone wolf. The West has missed out an important point - the formation of organised Christian extremism
Those who convientenly blame Muslims and Islam for "extremism" and "terrorism" should rethink and read the living history for truth, honesty and justice
The Moroccan occupation remains the last case of decolonization in Africa. The Moroccan military invaded in 1975 despite a clear ruling issued by the ICJ.