user: Question: Who was the challenger when winner was Kimio Nonaga?
Columns: ['Special', 'Original airdate', 'Iron Chef', 'Challenger', 'Challenger Specialty', 'Theme Ingredient', 'Winner']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Millennium Cup', 'January 5, 2000', 'Chen Kenichi', 'Zhao Renliang ( 趙仁良 Chō Jinryō ? )', 'Chinese (Beijing)', 'Abalone', 'Chen Kenichi']
SQL:

assistant: SELECT "Challenger" FROM "Table" WHERE "Winner" = 'Kimio Nonaga';