Shang Beida unwillingly lets Casper hold him back and lets his horrible father leave. He doesn't let his guard down, towing Casper (and Bob) along with him in the opposite direction, just to get away from that horrible fucker.

"Are you okay, baobei?" he demands once they're a hallway away. "He absolutely can leave this place without you, he can't have you. You're not a thing to be had, anyway, you're a person, and he's a dick, and I hate him so much holy shit. Sorry. I know you have more complicated feelings about him but my feelings are very violent."