Good work. I'd recommend pausing for a second when the giant rat appears to describe it. When I think 'giant rat' I think of an overgrown rodent, not one the size of a man. I'd add a single line as a new paragraph to describe how abnormally large it is.

And later, when the other rats show up, I'd also add another line to point out their size, both to contrast against the giant rat and the the smaller one, and to clarify that these are rodents of regular size.

Other than that, this is shaping up to be a fun story.