Faust thinks he's gone mad after the death of his daughter, Arhea, because he'll do anything to bring his precious child back to life. A talented alchemist with amnesia about his past, Faust can summon his "daughters," Homunculi.
By pretending to love them and making them work in the village, they grow, their souls becoming stronger in an emotional affinity, then comes the time to sacrifice them to harvest the emotional essence of their souls.
With a number of emotional essences of joy, fear, sadness and anger, Faust is sure to be able to resurrect Arhea. All he has to do is infuse her soul with the essences on a full-moon night.
His first attempt at resurrection was a failure, but Faust doesn't give up. He continues to create his "daughters" and sacrifice them. Faust feels no remorse in killing the Homunculi, even though they have emotions, like humans.
Every full moon, he tries to resurrect Arhea, but to no avail. Faust is unable to target the exact number of emotional essences needed to bring his precious daughter back from the dead. But he doesn't give up.
One day, he created a mistake. A Homunculus whose body barely holds together. He immediately despises her, but he doesn't kill her, because she can still bring him money by working.
Mistake, that's the name she's given herself, has the personality of a learning-disabled adult. She speaks slowly, says only a few words, but she's no fool. She knows what Faust is planning to do with his other "daughters," but she’s unable to warn them. Besides, they love "Daddy" so much that the idea of him killing them makes no sense. Mistake never calls him "father" or "daddy," only "Faust."
While Faust leaves the house, on days when she's not working, Mistake enters the room he calls the "forbidden room," because Homunculi are not allowed to go there. This is the room where there's a summoning circle, Arhea's body, safely placed in her bed, a large book on a table, and a "chamber" containing the child's soul.
Mistake manages to speak with Arhea's soul and soon discovers that something is amiss. This soul is not that of a child, but that of a grown man, a powerful warlock and alchemist.
The soul gives Mistake a special feeling. It's the only talent she has, "sensing" souls, and she's hidden it from Faust. This feeling. Mistake has felt it before. From Faust.
Mistake's mind then understands The Truth. Who is Faust, who is the mysterious Master Warlock, an infinite cycle, an endless time loop. Barely able to keep her soul from tearing itself apart, she hatches a plan. A plan to end it all.
Weeks go by and another full-moon night begins. Faust enters the room where Arhea is, unaware that no sound can be heard in the house. As if he were alone. Yet all six rooms are occupied by one of his "daughters."
He infuses his daughter's soul with accumulated emotional essences. The soul goes into Arhea's body. Like a miracle, she opens her eyes. Faust goes into her arms.
"My daughter! Oh, how happy I am to have you back!"
"Me... too... Faust."
"What?"
Suddenly, Faust cries out in pain as a knife is thrust into his back.
"Arhea? Why?"
"I... am... not... Arhea..." Said his ‘daughter,’ removing the knife and stabbing Faust again. "I... am... Mistake."
"Mistake? Mistake... no, that's not possible!"
Faust calls on his Homunculi to save him, but no one comes.
"My daughters, HELP ME!"
"They... are... dead... Not... coming."
"Dead? But I didn't kill—"
"I... kill... them... to... fortify... myself. Plan."
"Plan? What plan?"
Faust grew weaker and weaker. Mistake tells him everything. How his disdain for her pushed her to "grow up" on her own. To discover that he sacrificed his "daughters" to resurrect Arhea. To discover her gift of sensing a unique feeling in every soul. Braving the forbidden to chat with the soul in the "chamber." The future Faust’s, the Master Warlock’s soul. How an infinite cycle, an endless time loop, was created for Faust to become the Master Warlock.
"But HE killed my wife and daughter!"
"Future... you... yes... then... given... memory… loss."
Faust is amnesiac, after all. It makes sense, but he doesn't believe Mistake. Mistake continues to explain her plan.
On the day of the full moon, after all his "daughters" had returned from work, Mistake killed them to strengthen her soul. Then, Mistake went to the forbidden room, freed the soul from the "chamber" and killed herself so that her soul could take its place. She was careful to leave a knife in Arhea's clothes before taking her own life.
"Everything... was... ready... Faust."
"I put... your soul into—"
"Yes... now... the... cycle... end."
Mistake stabs Faust again and again until he dies. With his death, the time loop is broken.
Mistake, now human in Arhea's body, leaves the house. A new life begins for her. A happier life, she hopes.