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Aikido practitioners ( commonly called " aikidōka " outside Japan ) generally progress by promotion through a series of " grades " ( " kyū " ) , followed by a series of " degrees " ( " dan " ) , pursuant to formal testing procedures .
 Japan
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Japan