Sin: Nanatsu no Taizai, also known as Seven Mortal Sins, is a fantasy anime series that explores the story of Lucifer, a fallen angel who is cast into hell. There, she encounters and challenges the Seven Mortal Sins, each representing a different vice. The series is known for its blend of action, adventure, and supernatural elements, along with mature themes. The anime is distinct from the similarly titled 'The Seven Deadly Sins' series.