Sony's genre redefining first person shooter Killzone 2 went on sale in Japan yesterday, to a reasonable amount of success. Though first person shooters aren't nearly as popular in the East as they are in the West, the title sold 20,000 copies it's first day, and is on track to out sell Resistance 2, which sold 33,000 it's opening week. Further, reports are indicating that the game is selling out at some retailers. The Killzone 2 servers were updated earlier this week to allow for the influx of Japanese players in the game.