Sin has raceless white skin with long, mildly wavy, mint green hair. Her bangs are straight cut and swept to the side. A white flower with green leaves is tucked in her hair, as well as attached to her right sleeve. She has red eyes. Strung around her neck is a large golden key of unknown purpose. She wears a long white turtle neck dress with ruffles on the hem. The inside of her dress is yellow, and she wears a frilly green cape tied with a large bow of the same color over her dress. Her bottom half is that of an olive green serpent with the under side being light brown.
Not much is known about Sin's personality (as she has not appeared in any stories as of yet) other than she is kind and extremely loving. She accepts her wife's relationship with Lzet and is described to "understand perfectly that one can love multiple people." 
Not much is known about her past.
- Seaside Dispatches 1 Sin makes a brief appearance together with Reficul near the end of the manga, as well as during the Bonus Comic that also features their son Mors.
Sin's wife and lover. The two are extremely close with one another.
Her son. The two are very close.
- Sin is based on the serpent from the Bible that deceived Eve into eating the forbidden fruit.
- Her name means "an immoral act considered to be a transgression against divine law," which is commonly used in the Bible to proclaim an unlawful act against God.
- Sin is also a Thai name meaning "money."
- She is also based off of the daughter of Satan in the story Paradise Lost, who so happens to share the name Sin. In the story, Sin is described to have lower half of a serpent and the upper half of a beautiful woman; she has been described to have been surrounded by hellish barking dogs, and across from her is her phantomish son, Death (Mors).
- Sin has been drawn in a lake before surrounded by hellish dogs.
- Mors, her son's name is the Latin noun for death, as well as being the embodiment of death in ancient Roman myth and literature.
- In her character portrait, Sin is seen wearing a key; Sin, in the story of Paradise Lost, is the guardian of Hell's gate. The key she wears could prefigure to her being a gatekeeper in Hell's realm.
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- "Reficul-sama ♡"