The 46-year-old Date, who retired in 1996 and came back in 2008, announced last week that this would be her final tournament. She said in a blog that she has been hampered recently by pain in her knee and shoulders. She had a second surgery on her left knee in April 2016.
"I could not play my game but tried to win," Date said. "It's a big memory for me to play in Tokyo. The fans here support me a lot, and of course my friends were here and my sponsors were here so it was exciting."
Date won eight WTA titles and reached the semifinals at the Australian Open, French Open and Wimbledon. She reached her highest ranking of No. 4 in late 1995, behind Steffi Graf, Monica Seles and Arantxa Sanchez Vicario.
Also, Miyu Kato beat Nao Hibino 6-3, 6-4 while Magda Linette defeated Risa Ozaki 6-1, 7-5.