Being the Honorary Patron of the Japan Football Association, Princess Takamado has attended all FIFA World Cups since 1998. She has become the first member of the Japanese Imperial Family to visit Russia since World War I.
"Her Imperial Highness Princess Takamado is the Honorary Patron of the Japan Football Association. She has arrived in Russia to attend the games of the national team," an employee of the Japanese embassy said.
Local authorities have prepared a cultural and excursion program for the princess, who is expected to stay in Saransk, around 320 miles southeast of Moscow, until Wednesday.
Earlier on Tuesday, Princess Takamado visited the Mordovian Erzia Museum of Visual Arts, which holds the world's largest collection of more than 200 works by Russian sculptor Stepan Erzia.
"This is the first visit of a member of the Japanese Imperial Family to Russia in 102 years. Hisako Takamado is the honorary chairwoman of the Japan Football Association and arrived in the capital of Mordovia to support the Japanese national team during the match against Colombia," the tweet says.
The game in Saransk took place at the 42,000-seat Mordovia Arena at 3:00 p.m. Moscow time (12:00 p.m. GMT).
Japan, which has twice made it past the group stage at FIFA World Cups, will take on Poland and Senegal in their other two Group H matches.
The 2018 FIFA World Cup will come to an end on July 15, with the final set to be played in Moscow.