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Upon his return , he formed his studio Dive to Dream Sea and began work on Ragnarok ( for Champ Comics ) , one of the top-selling manhwa of all time , which he continues to work on to this day .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
Answer:
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