Mozaik Role (Manga)

is a Japanese manga series illustrated by akka that is based on the vocaloid song of the same name by DECO*27. 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 DECO*27's popular Vocaloid song "Mozaik Role":

Megumi Nakashiro never believed in doppelgangers or any of that occult stuff. Sure, she was a member of the occult club, but that was only because her boyfriend Kubohara was in it. However, her view starts changing when her boyfriend suddenly disappears and a girl named Megumi Kokusenya joins her class..

(Source: Manga Updates)