The Climax Series (クライマックスシリーズ, Kuraimakkusu Shirīzu) is the current annual playoff system implemented by Japan's Nippon Professional Baseball (NPB). It determines which team from the Central League (CL) and from the Pacific League (PL) will advance to compete for the championship in the Japan Series. After the creation of the NPB's two-league system in 1950, the PL experimented with three different playoff systems. In 2004, it implemented the postseason structure from which the Climax Series is based. After three seasons, the CL adopted the same system in 2007, creating the current, unified playoff format.