user: Question: Who was the opponent at GCM – D.O.G. 4?
Columns: ['Res.', 'Record', 'Opponent', 'Method', 'Event', 'Round', 'Time', 'Location']
Types: ['text', 'text', 'text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['Loss', '19-9-4', 'Naoyuki Kotani', 'Submission (armbar)', 'Pancrase - Impressive Tour 9', 1.0, '1:44', 'Tokyo , Japan']
SQL:

assistant: SELECT "Opponent" FROM "Table" WHERE "Event" = 'GCM – D.O.G. 4';