In Junji Ito's "Tomie" manga series, the origin of Tomie as a monster or supernatural entity is not explicitly explained. She is introduced as a mysterious and alluring character with regenerative abilities, but her true nature and origin remain shrouded in mystery throughout the stories.
Tomie's character embodies elements of horror and malevolence. She has the power to manipulate people's emotions and desires, often leading them to commit dark and violent acts. Her ability to resurrect and regenerate from even the smallest piece of her body adds to the sense that she is an otherworldly and immortal creature.
The lack of a definitive explanation for Tomie's monstrous nature is intentional, as it adds to the enigmatic and eerie atmosphere of the manga series. The focus is more on the horror and consequences of encountering Tomie rather than revealing the exact details of her origin.
As a result, readers are left to interpret and speculate about the true nature of Tomie, contributing to the enduring fascination and terror surrounding her character.