Demon Girl - Tale of a Lax Demon - Book 4 - The Demon Princess

She had a dream: the world was brimming with light. Family. School. Friends. Trains. Buses. Movies. Books. In that world of light, she grew into adulthood… and at the very end, in a white room, she fell into darkness. She awoke from the dream to find that she had become a demon. In the demon world, she lived a carefree life until she encountered a powerful being.
After such a long time spent living as a demon, before she knew it, spreading in her heart was a yearning for that world of light. She plunged herself into a summoning magic circle that had appeared. Then… when she opened her eyes once again, she had become a human baby.