The story consists of a group called "Dawn" trying to escape a place known as "Jail" which is an impregnable human asylum.
Tsuu is the protagonist and one of the Blood Maidens of Dawn. She is young with a strong sense of duty. When she was young, she vowed to marry Little Mermaid and acts as her prince due to it.
Little Mermaid is a brave girl who is also part of Dawn. She is gentle but can be impulsive. She also gets embarrassed about Tsuu's vow but still loves her nonetheless.
Jack is a boy that Tsuu and Mermaid found while trying to escape Jail. After protecting Little Mermaid from an attack, he almost dies but as he realizes his powerlessness, he turns into a nightmare. Being a nightmare puts his intelligence at an infant-level but still carries the kindness that he originally had. Only Tsuu can understand him.
Mary Skelter 2 will release on June 28th in Japan. People who pre-order the game will get a love visual novel game called Rengokuto Mary Skelter. Check out the teaser website for it. There is also a limited edition that includes an art book, calender, bath poster, music CD, and PC/mobile wallpaper.
Mary Skelter 2 and the Mary Skelter: Nightmares remake will release on PS4 on June 28th in Japan. There is no word on a western release as of now.