The Kira Investigation is the attempt, started first by the ICPO and continued by L and the Japanese Kira Task Force.

The investigation faced many difficulties. Once the fact that Kira only needed to know a person's face and name to kill them was revealed, the vast majority of the task force left the case. This desertion left only six task force member and L. Soon after, L temporarily enlisted the help of the FBI to investigate the possiblity of one of the task force members or their family members being Kira. Shortly afterwards, these agents died. Eventually, L approaches Light Yagami and has him join the task force.