According to Japan Today, Kou Shibasaki is one of the highest paid television actresses. The reason for Kou's success on television is the acceptance accorded her by the female audience. Because women make up a majority of the viewership in Japan, one has to be well-liked by this group to be popular on the small screen.
Kou was never a child idol like Aki Maeda or Chiaki Kuriyama, her co-stars from Battle Royale. As popular child idols, Aki and Chiaki spent years posing for photobooks and their names were used widely during the Battle Royale marketing campaign to draw in their fans. As a virtual unknown at the time, Kou's name had little currency. However, thanks to Battle Royale, Kou leaped ahead of both Aki and Chiaki in terms of popularity and to this day, Aki Maeda and Chiaki Kuriyama can't compare with the supreme popularity of Kou Shibasaki despite years and years of fanbase building.