The Piano Tuner who was once a member of the Royal Court Orchestra. The Pianist to be precise. Berthierite is under the orders of the Senate to rid for them unwanted enemies under the name of Accordeur. With the mask of a cat and what looks like a long double sword he attacks the royal orchestra without mercy. He was thought to be dead by Lucille, since he slit his own throat during a battle with guignols. But was confirmed to be alive in Volume 2, although it is unknown how he was resurrected. There are black crack marks around his left eye and across his scarred throat, hinting that he is contaminated with the Galatea Syndrome; the contamination may be contained, since the Senate is implied to have very advanced medicine at their disposal.
Berthie seems to be rather capricious and sadistic, toying with Lucille's emotions and claiming that he only wants Eles as a sister-substitute instead of as a true friend, as well as tormenting Carnelian by pointing out that the Rhodonite family had discarded him.