When first we meet him, Léon is kind of the male equivalent of Emma. He’s young, attractive, idealistic, and romantic to a fault. He’s also incredibly bored with small-town life in Yonville, and looks forward to the day when he can escape to Paris to pursue his law degree. Léon is initially a young man with dreams of romance and love, but is totally inactive – he’s afraid to tell Emma that he loves her, and instead pines after her until he leaves Yonville.
After he returns from Paris, however, Léon is a different animal. His experience with the worldly women of the capital have removed the veils of his tender fantasies; he no longer dreams delicately of his beautiful, untouchable passion for Emma. Now, Léon isn't satisfied with awkward flirtation. When reunited with Emma in Rouen, he goes straight in for the kill, flattering her with tales of his lovelorn misery, and inwardly plotting his conquest. Like Emma, Léon gradually loses his fairytale illusions, but never loses his desires – and like her, we get the feeling by the end of the novel that life has sullied and corrupted him.