C-Kira

C-Kira (シー-キラ, Shī-Kira) is the user of Midora's spare Death Note.

Character
C-Kira is noticeably different from other users of the Death Note in the series, as he only kills the elderly that wish to die. It is known that C-Kira made the trade for the Shinigami Eyes. It is apparent that his will was not very strong, as after Near says (as L) that C-Kira is an "abominable murderer", C-Kira committed suicide.

Plot
C-Kira is the name given to the third Kira by Near, which stands for Cheap Kira. He is named as such because he only kills the elderly that wish to die, which is similar to assisted suicide. Near has no interest in pursuing the case, citing his lack of personal interest, calling C-Kira an "abominable murderer".

Rejected by Near, C-Kira suddenly stops writing names into the Death Note. Midora returns to the Shinigami Realm, telling Ryuk that C-Kira "let out a squeal" and wrote down his own name in the Death Note. Ryuk then tells Midora one of Light's statements: "The person that is chosen to use a Death Note must have a strong will in order to truly perform divine justice like Kira."

Trivia

 * The film Death Note: Light Up the NEW World introduced a physician named Alexey lvanov who serves as a loose adaption of C-Kira. In the film, Ivanov begins a campaign of assisted-suicide all across Europe.