It was three months ago when Souka suffered a seizure... The name of the illness is the "I-Type Vibeil Outbreak." To summarize the illness, it basically multiplies the antibodies inside of her body by enormous amounts, causing the antibodies to attack her own body, which will eventually lead to her death. There is no cure for this illness, but there is one treatment. That is to deliver her antibodies to another patient, Cildy, by biting into her body to transfer the antibodies. Cildy also carries an illness called the "Louge Golge Syndrome" which is the complete opposite of Souka's I-Type Vibeil Outbreak and Cildy carries no antibodies, which will cause her to become vulnerable to diseases. The two need each other to survive, but they notice as time passes that Cildy is becoming weaker and weaker. At the same time, Souka hints at a secret that Cildy carries with her. That secret veils all the facts about their diseases...

It was in the year 2800 of the Midgard calendar. Back then, there was a Overlord who once reigned supreme and had reached the very brink of subduing the world. Her name was Ruphas Mafahl, a great woman dreaded as the Black-Winged Overlord. She was too strong, too fast, and too beautiful… However, she was defeated by Heroes who opposed her ferocity, and her ambition was brought to an end. ――or so went the story of our protagonist’s in-game character, whose body he now possesses for some reason in a world 200 years after Ruphas’ downfall. Follow our protagonist as he becomes unnecessarily feared by his surroundings and unnecessarily worshiped by his former subordinates as he―or now she―cheerfully travels around this fantasy world.