Shiryoku Kensa (Manga)

is a Japanese manga series illustrated by Tama and featuring storyboards by Chano. It is based on the vocaloid song of the same name by 40mP. The manga was serialized in the COMIC@LOID magazine and published in Japan by ASCII Media Works under the Dengeki Comics NEXT imprint from January 2014.

Synopsis
Based on the 40mP million-view hit Vocaloid song Shiryoku Kensa, Miyashita Megumi, also known as "Gumi", was one of the only survivors in a plane crash thirteen years ago. Since then, she has been able to see two copies of every person and one of them always has a "C" on them. Thirteen years later, she now wears glasses, yet her left eye remains a puzzle. And then, her friend goes "missing".

(Source: Chinatown KM)