Sick Mind is a Yume Nikki fangame produced by marisyan.
It started out as a fangame with only one main character, but in it's remake; it now has three main characters to choose from.
Kurayami - Has purple hair
Yamitsuki - Has black hair
Iratsuki - Has green hair
They each have their own stories within the game.
Download the current version here
The remake is currently at version 0.00