Board Thread:Questions and Answers/@comment-27253428-20160411001620/@comment-24947676-20160411191949

From what I understand, here's the story.

Note: This is just an interpretation.

Some time ago, Len, a baku, met a Gumi with the initial intent of eating all her dreams and nightmares, but fell in love with her. At some point she fell into a deep sleep (wether or not she's dead is unknown, but it's implied she died, but it's unknown how).

After this, he started taking the dreams of girls like Miku (in Yumekui, the girl is shown to have twin tails, so we'll just assume it's Miku) to give them to Gumi in the hopes that she'll come back to life.

At the end of the song, Gumi seems to be alive, so I guess Len's plan worked?

It seems to be really up to interpretation.