I would expand a bit this thought process from him hearing he will live in a land of dragons to saying “I’m ready” doesn’t really feel the natural first response. I’d have him think about it somehow or even just be like dragons? Or go why? Or even a more natural response like,
He thought about it and he didn’t have anything to lose, so even though this whole thing felt like maybe just a hallucination, he was sure maybe he just breathed in too much smoke or hit his head and would wake up in a few minutes, he decided to agree to it.
“I accept your challenge. I’ll do it.”
Something like that feels more natural
You could maybe say, Lost in his thoughts, he didn’t notice the commotion going on around him until suddenly he heard the sirens. When he looked up, people were screaming etc
That would make a smoother transition
This paragraph was a bit jumpy to the next one. I’d say it seems like he walked really slowly when the world around him went really quickly. Since he just walked outside and already all of this is going down. In that case maybe we need to see him sit down somewhere or zone out more to allow that time to pass. If that makes sense.