Engi Three-Piece, a dream demon consumed by vengeance, hunts Pharos Hercules for orchestrating her sister Patti’s demise. Pharos lured Patti into the human world, leading to her fatal betrayal—a loss that shattered Engi and withered their once-vibrant shared dreamscape into a desolate expanse.

Emerging first as an adversary, Engi clashes with Merry Nightmare under the false assumption of her loyalty to Pharos. She commands a lethal dance of blades, anchored by her signature weapon *Sannasubi* (Violet Flash in the Moonlight), which multiplies endlessly within her moonlit wheat-field domain. Her power here hinges on two constants: swirling winds and the pale glow of moonlight.

To traverse the human world, Engi bonds with Yui Kounagi, a girl who willingly becomes her host. During possession, Yui’s eyes sharpen and her demeanor hardens, signaling Engi’s control. Though merciless to foes, Engi strictly shields Yui from harm and spares innocent humans, binding herself to a self-imposed code of honor.

Guilt gnaws at Engi for failing to protect Patti from Pharos’s influence. This anguish softens as an uneasy alliance with Merry and Yumeji Fujiwara disrupts her vengeful obsessions. Yui’s steadfast companionship further quiets Engi’s storms, weaving a fragile trust between them.

Her path intertwines sacrifice with redemption, torn between retribution and safeguarding Yui. When missions threaten her partner, Engi hesitates—choosing Yui’s safety over vengeance, a shift from solitary fury to shared resilience.