He continues to talk politely and not eat anyone. 

When the magical girl shows up, he offers the same polite nod and "Hello!" he's given other arrivals. 

"- gosh! I was not expecting - wow - I've never seen you around before, have I?"

"Nope! I am new. Sent here from another plane of existence by a very different kind of magic than yours, as near as I've been able to tell. Magical girls such as yourself were a surprise to me, though not an unpleasant one." 

"A different plane of existence, wow, what's that like?"

"Diverse! Humans, and dragons like myself, are only two of the many species that live there. Also, sadly, in grave peril at the moment, due to an invasion of extraplanar beings, a situation which was indirectly responsible for my exile."

"You're exiled? Whoa."

"Insofar as I don't seem to have a way to get back, yes. The magic that sent me here was intended to aid in the war effort, and it may yet do so, but this was not an outcome anyone foresaw." 

"...how would it aid in the war effort, are you trying to recruit people here?"

"I am a warrior of no small ability, dedicated to repelling the invaders, and my kind grow stronger with age. An ally proposed to...force the issue...by aging me with a notoriously finicky kind of magic, and I suspect this resulted in my being shunted to a place where time passes more quickly. That is my hope, at any rate, as I doubt I'll otherwise be able to return before the war is over."

"Time passes more quickly here? That must be weird for you."

"I suspect it runs faster here than in my plane of origin, but even if it does, I would not have a way to notice this fact unless I could see both at once...there are indeed many things about this place that surprise me, but time is not one of them.

"To be clear, none of this is germane to my presence in London, specifically. I'm here because the local abolitionist faction appears to be doing Good work and I would like to see if I can aid them in it."

She wrinkles her perfect nose. "Why?"

"I abhor slavery. It causes great suffering to the victims and is often detrimental to the souls of slave-keepers besides."

"It's so... political."

"A great many things worth doing will often touch on the subject of politics. It can be frustrating at times, but such is the way of the world."

"Fighting monsters is worth doing and just helps everyone, no politics about it."

"Indeed it is! I intend to do a good bit of that as well. It was my main interest, before I came here, that and improving my combat skills. What is your specialty?"

She fires off a silver ray of light into the air. It makes a whistling sound. "That. Great for shooting monsters with."

"It looks it! I know many a warrior who would envy the ability to use such magic reliably. Ours tends to have a recharge time, though there are exceptions. Perhaps you'd care to spar sometime?" 

"I don't know about that, you could bite me in half!"

"I wouldn't use any lethal moves, that would rather defeat the purpose of a spar. More like, can I tap you with the tip of my tail before you land some number of hits, practice aim and dodging and such. I could also serve as a monster-substitute to help you and allies practice teamwork, I can be very difficult to lastingly harm."

"I'm not sure if those even hit non-monsters, to tell you the truth."

"In some ways that's better, I suppose, since you'd be able to see if it would hit. Does it carry an effect of some kind, or just put holes in things along the path of travel?" 

"With monsters they kind of shrivel up for a ways around where I hit them."

"I think I'd rather not be the first non-monster to test it, then. Perhaps a tree."