As seen in videos, supporters of the "Samurai Blue" carried waste bags and roamed around the stadium to pick up all sorts of the litter left by spectators.
"We are not too euphoric because we do know there is going to be a hard match against Japan", Senegal coach Aliou Cisse said.
Senegal kick-started their Group H campaign with an impressive 2-0 win over Poland, 16 years after first appearing in the World Cup in 2002.
Senegal manager Aliou Cisse says he is "certain" an African team will eventually win the World Cup.
A Japan-based football journalist, Scott McIntyre, told the BBC that cleaning up is "part of Japanese culture".
"I am the only black coach in this World Cup".
The gesture wasn't just extended to fans in wheelchairs, either - according to GNN's Russian correspondent, Timofey Yakovets, the sombreros were basically just being given to any person who shared their love for the World Cup. It is a habit drilled into citizens from a young age, with students expected to clean their school classrooms and hallways.
The fans, draped in Japanese flags and scarves, were filmed sweeping the stands of the 44,000-seat, bowl-shaped Mordovia Arena, where just a few minutes earlier they had wildly celebrated an unexpected victory over José Pékerman's side, quarter-finalists in 2014. The Lions' next match is against Japan on June 24, and we will be enthusiastically watching and rooting for them.
They showed up at the World Cup match sporting trash bags.