ییوری کیللیان

Yuri, like Layla, is an experienced performer, yet he's deeply traumatized by a terrible tragedy. During a flashback, it is revealed that his father died attempting the Mystical Act, and he never forgave Kalos for letting his father try.

[Spoiler: Yuri plays a pivotal role in the second half of the first season when he betrays the stage, first by stealing away a good portion of the cast and later by buying out the stage and taking control of it. He later agrees to return it to Kalos if Layla and Sora accomplish the same Mystical Act that caused his father's death; when they manage to do so, he fulfills his promise.]

In the second season, Yuri helps Sora get into the Circus Festival in Paris. He appears to be a bitter rival of Leon's, and feels that he is responsible for the death of Leon's sister.

(wikipedia)