In Gensokyo, Reimu Hakurei herself undergoes an anomaly.
The massive negative feelings she has been receiving from both humans and non-humans have built up to the point where she can no longer stand it in her human body.
So, Reimu creates another self to separate herself from this root of evil... and challenges her to defeat her. However, even with all the power of Gensokyo, the root of evil could not be destroyed.
Unable to stop her, Gensokyo expels M-Reimu (Maga Reimu) into another world. 