The sight of Japanese fans at a World Cup bagging trash after a match - win or lose - always surprises non-Japanese. Japanese players are famous for doing the same in their team dressing room: hanging up towels, cleaning the floor, and even leaving a thank-you note.
The behavior is driving social media posts at the World Cup in Qatar, but it's nothing unusual for Japanese fans or players. They are simply doing what most people in Japan do - at home, at school, at work, or on streets from Tokyo to Osaka, Shizuoka to Sapporo.