His overconfidence

Leon was walking in a relaxed manner towards the main door to welcome Sean. He knew Sean couldn't stay with Aeon who would restrict him from a lot of things and activities. 

He has spoiled Sean to the extent, if anybody tries to speak about morals or his behavior, Sean just snorts and walks away by rolling his eyes.

Since Sean was returning after Eliza went to Aeon's place, Leon was expecting Sean to bring her back too. He had deeply sowed the fear in her, it had grown to a huge tree so she wouldn't dare to speak anything about him to Aeon.

Leon was certain about that. And he was pleased with himself for having total control over Eliza who knew a lot of secrets about him and Sean who could be used to weaken Aeon anytime.

Nonetheless, his happiness wasn't fated to last long. 

Why did he even expect to have some happiness especially after 'Ava Kelly' returned to turn his life upside down?