"The only thing humans, rats and crows have in common is garbage," announced Ryuta Ushiro, leader of artist unit Chim ↑ Pom, with a mischievous smile.

Before I had a chance to suggest some others, a sudden and very unhuman scuffling sound at the back of the gallery made it clear that this was no time for pedantry. Whatever incongruous conclusion these wacky artists had drawn from their dodgy "discovery," it had already been played out. All that remained was to step inside Hiromi Yoshii gallery and survey the damage.

I say "damage" because in the three years that these guys have been working together, they have gained a reputation for art that shocks as much as it inspires — and horrifies as much as it entertains. Just last month, they deliberately flooded the basement gallery at book store NADiff in Ebisu. Earlier this year they were flinging garbage from a helicopter onto a community in Bali that subsisted on recycling. What had they done now? And, importantly, what did it all mean?