When Sugimura is looking for Kotohiki, he activates his scanner to see if she is nearby. The scanner shows her location, but fails to show either Mitsuko or Kiriyama, who show up quickly after.
In the film, the two transfer students are Kiriyama, the silent killer, and Kawada, the winner of a previous Battle Royale. In the original novel, only Kawada was the transfer student; Kiriyama was in the same class selected for this game of death. He was the main antagonist.