Original: Kira Game is a strategy game where the player takes on the role of Kira or L/O. These are just titles, as any character can be Kira or L/O. The player will attempt to deduce who their enemy is (Kira will try to uncover L's identity and vice versa).
Simplified: After L dies, two more people fight to catch Kira, and for the name of the second L/O. They lived in an orphanage and were competing to be the next L/O. One of the people fighting finds out that Light is Kira, leading to Light's death.