C-Kira

C-Kira (シー-キラ, Shī-Kira) is the user of Midora's spare Death Note, which was received by bribing the Shinigami King with thirteen apples brought back from the human world. His identity is still unclear, as it was never once revealed in the entire manga one-shot special. It is also unclear whether Midora chose this person or merely dropped her Death Note in the general vicinity.

Character
C-Kira is noticeably different from other users of a Death Note in the series, as they kill elderly that wish to die. It is known that C-Kira made the trade for the Shinigami Eyes. It is apparent that their 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 them by Near, which stands for Cheap Kira. They are named as such because they kills only 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 their 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."