He is a Special Class Investigator of the CCG and is infamously known as the White Reaper. He has served the CCG for over eighteen years and is widely considered to be the most skilled among the other investigators. Unknown to them, however, Arima is actually the One-Eyed King, cooperating with Eto Yoshimura and Aogiri Tree. Together, he and Eto plan to raise Ken Kaneki as Arima's successor as the One-Eyed King.