Alya Césaire (also known as Rena Rouge) is the supporting character of Miraculous: Tales of Ladybug & Cat Noir and the love interest of Nino Lahiffe/Carapace.
Alya saw Ladybug return with new ally in complete awe and then suspicion of how the hero spoke similar to her friend. After her sister Anansi had been saved Alya was amazed that a new hero entered the scene and asked for his name calling himself Carapace. Once Nino came back, Alya admits she saw what he did for her. In "Heroes' Day - Part 1", she unveils that she is Rena Rouge to Nino and that she was aware he was Carapace. When meeting with the other heroes they argue about covering each other.