Tohoshinki is not just a Korean act, they dominate Japan as well on a daily basis without having to lift a finger. Doesn't matter if you don't know them
As if time after release matters that much after 10 weeks. Fact is, Gaga and Katy are selling the same outside the US now, and both don't have a hit outside the US atm.
Japan is helping Gags, anyhow, Artpop still has a long way to go to reach Prism's total sales