Bleu is a member of the Gallia Knight Army, and brother to Damien, Jack and Jeanette. He is capable of leaping great distances and performing impressive acrobatic moves. Just like his older brother Jack, Bleu is a capable fighter and is good with a sword. He's seen taking down two royal guards with one swipe. Also he is a mage, he use his sword as an wand.
After stealing the Founder's Round Mirror, Bleu handed it over to Joseph of Gallia, still sour about his brother being arrested he is happy to fight Saito in order to allow his sister to capture Louise.
There is some speculation about his name, Jack referred to him as Bleu, but Jeanette referred to him as "Leuleu," though regarding Jack's serious nature and Janette's rather carefree one, it is likely "Leuleu" is just a nickname.In season 4, he along with Damien, Jeanette, and Jack are hired by Tabitha to help defend against the Ancient Dragon at the magic academy. They help magical setup a shield around the school.