As Tokyo's millions put in another day's work on the coalface of capitalism, celebrity Marxist philosopher Kohei Saito and his friends are clearing rocks from a muddy mountain stream.
Saito's core argument — that capitalism is the root cause of climate change, and we need to stop chasing growth to save the planet — has struck a chord in the world's fourth-largest economy, especially among young people.
The associate professor at the University of Tokyo has sold half a million copies of his latest book and last month spoke at music festival Fuji Rock, headlined by The Killers.