User blog comment:B214/High School DxD BorN episode 1 review/@comment-3965848-20150406162137/@comment-24502975-20150406174534

Oh, that part. Hmm. Right now the only possibility I can think of is Tannin's return to begin his training with Ise. A dragon that large landing near the castle might create some light shock waves or something.

...Now that I think about it, I can't even imagine anime-Tannin flying with wings...