The world number five is joined by compatriots Tatsuma Ito, Go Soeda, Taro Daniel and Yoshihito Nishioka at Roland Garros, the biggest contingent of Japanese men at the event since in 1967.
Nishikori believes that this strong presence in France indicates that the game is in good health in his home country.
"It's great to see many Japanese players here and I think men's tennis has gotten much better right now in Japan," the 25-year-old told the official ATP website.
"Those two young guys, Taro (Taro Daniel) and Yoshi (Yoshihito Nishioka), are playing great tennis. They qualified for the US Open too. Now they qualified here, so it's great to see for Japanese tennis."
Nishikori began his French Open campaign with a victory on Sunday, downing Paul-Henri Mathieu 6-3, 7-5, 6-1. Soeda was not as fortunate as he was beaten by Phillip Kohlschreiber in straight sets.