http://www.4gamer.net/games/128/G012841/20111003040/Just a summary of the official website's updates and some character profiles. Still in Japanese but text form so you can google translate that if you want. Bad summary of what I got of the story,
In the year 20XX
it's widley accepted that science can disprove any strange phenomena in the world. However in later years rumors begin to emerge about 'Cannibal Shadows' aka UNREAL BLACK THINGS. If a human has his own shadow eaten by the Shadow, they become Night Hollows that forever wander the earth as dead zombie things.
Hyde's your typical sword-wielding Japanese highschooler. No real interest in trivial things and doesn't give a crap about some silly rumors of cannibal shadows, yet somewhere in his heart he yearns for excitement and adventure in his life. As luck would have it, one day while walking home from school Hyde encounters an UNREAL BLACK THING quickly approaching him. Linne, a girl on a mission, encounters Hyde by chance and saves him and they form a companionship to fight off the remainder UNREAL BLACK THINGS.