Campione
Godou Kusanagi
Circe fell in love with Godou to the point that she willingly gave him some of her power when he defeated her, because she feared her body was so injured that Godou wouldn't gain an Authority from her death.
Black Prince Alec
Circe fell in love with Alec when he visited her island home, but her feelings seem to have faded with his leaving her, and severely wounding her.