Gamindustri......a beautiful world where 4 goddesses resides with each nations; Planeptune, ruled by Purple Heart. Lastation ruled by Black Heart. Lowee, ruled by White Heart. And lastly, Leanbox, ruled by Green Heart.
What if a global pandemic spreads throughout the 4 nations of Gamindustri? Caused by an evil organization who hates the goddesses and plans to dethrone them by launching a project called "Project Twilight". With the project gone wrong, the pandemic is called Blood Twilight.
3 years later after the incident, follow the story of Adrian Leonhart, a former hunter of Lowee, a lone wolf bounty hunter, who strives to survive, to find answers on what happened to his sister, whether she is dead or alive, he will do whatever it takes to seek the truth.
One day, he saves a girl called Nepgear from being held captive, and Adrian has this strong urge to protect her at all cost because he reminds Nepgear of his sister.
In the year 2006, Lastation just finished having their latest shift period and Noire a.k.a. CPU Black Heart is now the nation's goddess. Without a proper Oracle to guide her, she is forced to resort to her own intuition. Finding and instantly forcing a friendship with a lost knight named Claire, she faces many enemies that are keen on destroying what she was forced to care for.