Rui Salacia Dantalion is a fallen Tetragrammaton nun. She is the daughter of Rhadamanthys and Phoenica, and the sister of Renn. She is also known as Rui Mikagami (水鏡 泪 Mikagami Rui).

She was sent to a Tetragrammaton monastery at a young age. She chose the temple sword because she knew her brother was studying armsmaking. Having a long study in the monastery made her a strong believer of the Tetragrammaton. After she finished her study, she intended to look for her brother. Hearing rumors that her brother had gone to meet Dreamweaver made her want to protect him. Rui likes to preach. Her sermon usually attracts men, young and old.

Rui is previously named Riviera Belladonna. She is 161 cm tall and weighs 50 kg.