I mean, he locks her in a cage because if he doesn't "he didn't know what she might do next." Like WTF. He's treating her like she's some wild animal. And even though he claims later that the door was never locked, I don't really believe it. That was incredible creepy to me. And then the more I thought about it, the king is like that for the entire story. Controlling, manipulative, withholding info, lying, making romantic sounding excuses for his behavior, intentionally making her uncomfortable... Yeah, I know he's the wolf king and that's the idea of his character, but I like Yuurin a lot, and she deserves more than receiving a love confession while locked in a prison that the man she loves put her in.