Summary: In the twisted heart of Hell, demons climb over one another for power, but Danielle Marsh is different. The daughter of Belphegor-the Demon Prince of Sloth-she is known as the "Sleepy Princess", a being of terrifying power and even more terrifying laziness. She refuses titles, responsibilities, or anything requiring more energy than a sigh. While her father sleeps on a throne of bones, Danielle dreams beneath dead stars, snoring through centuries of chaos. Frustrated by her refusal to contribute, the higher powers of Hell try to banish her to Earth-but she's too strong, too stubborn, and too sleepy to be moved. Until a wish breaks through the veil. Haerin Kang, a quiet, diligent high school girl, has reached her limit. Bruised by bullying, crushed by family expectations, and suffocating under pressure, she lights a forbidden candle and sells her soul, begging for someone-anyone-to save her. And someone comes. Danielle appears in her bedroom, yawning, barefoot, wrapped in a cloud of feathers, and demanding a place to nap. Haerin groans. She summoned a useless, nap-loving demon who won't even open her eyes, let alone exact revenge. But there's something strange about Danielle. She only glares when someone touches Haerin. She scorches entire skies when Haerin sheds a tear. And sometimes, in the quiet before sleep, she whispers Haerin's name like it's the only thing keeping her awake. Together, they must navigate high school, soul-binding contracts, and the terrifying bond forming between a girl who gave up-and a demon who just might care too much. But how do you love someone cursed to sleep through everything... except your pain?

One night, after a heated argument with her mother Haerin, Danielle storms up to the attic in search of solitude. Dust blankets the old trunks and boxes, but what truly captures her attention is a worn leather journal tucked inside an old chest. The journal belongs to her mother, written when she was seventeen. As Danielle flips through the faded ink and fragile pages, she finds a group photo pressed between them. The faces are smiling, frozen in time-but one girl stops her heart cold. Jihye Marsh. A girl with Danielle's face. The resemblance is uncanny-too sharp to dismiss as coincidence. Confused and unsettled, Danielle reads until her eyelids grow heavy, clutching the photo in her hands. When sleep takes her, she awakens to a strange yet familiar world. The calendar says 1991. The clothes, the music, the slang-all different. The mirror confirms the impossible truth: she isn't Danielle anymore. She is Jihye Marsh. Here, Danielle meets her mother again-but not as "mom." Haerin is seventeen, the same age as Danielle, full of fire and unpolished dreams. Alongside Haerin are her friends Minji, Hyein, and Hanni-girls bound by youth, secrets, and the fragile thread of friendship. Danielle learns that Haerin and Jihye had been best friends, and as time passes, she discovers something else: Haerin had loved Jihye, deeply and silently. Torn between her role as Jihye and her identity as Danielle, she must navigate this fragile past while unraveling the mystery of Jihye Marsh's sudden disappearance. Was Jihye lost... or did she become Danielle? And if Danielle uncovers the truth, will she ever be able to return to her present-or will she vanish into the life of a girl who once existed?

..... Kang Haerin, after spending nearly five years of her youth locked away in a cramped prison cell, finally stepped out beneath the open sky once again. Fate, however, had other plans-leading her straight into the path of Danielle Marsh, an accident that would twist her life into something unexpected. Danielle, a seemingly ordinary young woman from Busan, couldn't shake the pull she felt toward Haerin after that one encounter. Even knowing where Haerin came from, Danielle's curiosity only deepened-for she carried secrets of her own. Secrets that made her question the very purity Haerin saw in her. "I thought I was complete when I was with him," "But then there was her..." And if that were truly the case, why did I find myself wondering, Is she as lonely as I am? Every time I looked into Haerin's eyes?

Haerin and Danielle couldn't be more different. Haerin is a small-town mechanic from Yeongpyeong, South Korea, fiercely dedicated to her garage and her quiet, simple life. Danielle, on the other hand, is a sharp-witted psychologist from Australia, used to city life and determined to stay as far away as possible from the cat-eyed girl who's suddenly sharing her space. Their worlds would've never collided-until fate threw them together under bizarre circumstances. Forced into a fake marriage, they're stuck living under the same roof, pretending to be a loving couple for the sake of appearances. What starts as a reluctant arrangement quickly spirals into chaos as living together isn't as easy as they thought. With their clashing personalities, noisy family members, awkward encounters that test their patience, and rules like "No meddling in my personal life" and "Stop stealing my coffee!" tensions run high. In a world where nothing about them makes sense, will this make-believe marriage lead to a genuine happily-ever-after? Or will their contract run out before they can figure it out?