Makai Wars was a Role-Playing Game in development by Nippon Ichi Software for the Playstation Portable, and was expecting a release date around the console’s initial launch in 2005. Development on Makai Wars was put on hold due to a number of internal conflicts, a few years later the title was announced for release on the Playstation 3, however it’s current status is unknown.
As we can read in Wikipedia, it’s interesting to notice that Makai Wars is frequently referenced as an internal-joke in other NIS games. In “Prinny: Can I really be the Hero?”, we find out that Asagi was to be the main character of the cancelled game, but was removed due to the ending of making the game. It’s one of the few reasons Asagi is insane in Prinny CIRBTH, mentioning it during a therapy lesson with the Hero Prinny.
Makai Wars is later mentioned in the PSP Version of Disgaea 2, in the special “Axel Mode”. In the story, Makai Wars is actually a movie, which has been on constant Hiatus and development hell. Also, in the graphic / text adventure game “Disgaea Infinite”, there’s a bonus ending in which Asagi try to buy a “time machine” to be able to change the her past and let Makai Wars to be released.
Thanks to Mittell for the description!