The Mary Skelter 2 Prologue is a collection of short stories detailing the original Little Mermaid story, Otsuu and Little Mermaid joining the Dawn, and the effects that that has had on the rest of the Dawn.
While this is titled as a "Prologue," it does contain spoilers for parts of the game, so it is recommended to read it after or during a play through, reading it as more information is revealed through the game.
Story 1[]
External Link[]
English PDF: http://ideafintl.com/images/MS2_Novel.pdf