Ruka (Western spelling: Luca) is half French and half Japanese. He is a childhood friend of Natsume and often referred by Mikan throughout the story as "Ruka-pyon". He has a gentle and pleasant personality that balances out that of Natsume. In chapter 48, after Youichi kisses Mikan on the cheek to say thanks, Ruka does the same but he asks Mikan to keep it a secret. Even Hotaru also knows about it and asks him to tell it to Mikan. He always carries around a rabbit as he has the animal pheromone Alice, so he can communicate with them. Ruka is liked by other students in the academy.
He belongs to the Somatic class and is a Triple Star student like Hotaru and Iinchou, but later throws away his stars, and becomes a No-Star, saying how light he felt without them.