Who Is Kei Nishikori?

A man holding his mobile phone walks in front of a poster of tennis players Kei Nishikori of Japan (C) and Roger Federer of Switzerland (L) outside a sports shop in Tokyo on Sept. 8, 2014. Tenth seed Nishikori is the first Asian man to reach a grand slam singles final while his opponent, Croatia's Marin Cilic, is also into his first final.

People cheer as Kei Nishikori beats Novac Djokovic at the semi final of the U.S. Open during a public viewing event at Nishikori's home town of Matsue, Japan on Sept. 7, 2014.

A man writes a message to Japanese tennis player Kei Nishikori on a board with newspapers reporting him in the U.S. Open, in Nishikori's hometown of Matsue, Japan on Sept. 8, 2014.

A sport shop offers bargain prices to celebrate Kei Nishikori's win over Novayk Djokovic at the U.S. Open semi-final in Osaka, Japan on Sept. 7, 2014.

Green Tennis Garden coach Masaki Kashiwai teaches his students during lessons in the hometown of Japanese tennis player Kei Nishikori, Matsue, Japan on Sept. 8, 2014.

Green Tennis Garden coach Masaki Kashiwai speaks during an interview in Matsue, Japan on Sept. 8, 2014. Kashiwai began coaching Nishikori when he was just six years old and quickly saw traits in the future star that separated him from the other players.

A girl practices serving at Green Tennis Garden in the hometown of Japanese tennis player Kei Nishikori, Matsue, Japan on Sept. 8, 2014.

MATSUE, Japan - Penguins in Matsue Vogel Park walk in costumes featuring Air K, the nickname for a leaping forehand shot of tennis player Kei Nishikori, ahead of his U.S. Open final in New York, Matsue, Japan, Sept. 8, 2014.

Girls walk near an advertisement of a sporting goods company with a picture of Kei Nishikori in Tokyo, Sept. 7, 2014.

Kei Nishikori, of Japan, reacts after defeating Novak Djokovic, of Serbia, during the semifinals of the 2014 U.S. Open tennis tournament in New York City on Sept. 6, 2014.