The World No 71 took just under 90 minutes to find her way past Hercog, forcing a single break in the first set and a double in the second to claim the win. Watson, who reached the third round of the 2012 Wimbledon Championships - her best ever Grand Slam performance -, will play either sixth seed Anabel Medina Garrigues of Spain or Italian Camila Giorgi in the next round.
Meanwhile, Britain's top-ranked female singles' player, Laura Robson, will play Greece's Eleni Daniilidou in her first round match. Should she beat her first round opponent, she will likely come up against local girl Kurumi Nara in the second round.
Australia's Samantha Stosur is the other big name in the main draw at Osaka and the 2011 US Open champion was similarly untroubled in her first round match against Japan's Erika Sema, winning 6-4. 6-2. Stosur won the HP Open back in 2009.
Japan had a poor day on the courts, with two other local favourites - Ayumi Morita and Kimiko Date-Krumm also bowing out, after losing to Jamie Hampton of the USA (3-6, 2-6) and Casey Dellacqua of Australia (3-6, 6-3, 4-6) respectively.
Aside from Watson, Robson and Stosur, Francesca Schiavone of Italy, the World No 33, is also in Osaka and is scheduled to play a qualifier in her first round match. If she gets past that game, she will play another Japanese entrant, Misako Doi, in the second round.
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