User blog comment:TheJudicialDoll/New Mothy Song - "White Brick and Black Mourning Dress"/@comment-110.54.148.218-20190909225434

At the end of the song, it shows Margarita, the Princess of Sleep.

My theory is that this is her story prior to the events of The Gift from the Princess of Sleep where she marries Marquis who no longer loves her and her son being the boy who ends up in Riliane's care, making him the little boy in The Response She Kept Waiting For