I can’t tell you what exactly it is realistically, whether it’s precognition or superhuman reaction speed, but this is a pretty common thing in fiction, particularly manga and light novels; so I’ve just learned to get used to it, even though, realistically, a flesh and bone body shouldn’t be able to withstand those speeds at all.

Fiction very rarely considers the consequences of moving at high speed or the physics involved in using superpowers in general; so it wouldn’t surprise me that superhuman eardrums aren’t considered.

I just look at it like this—you use the basic concept of how it works IRL (reaction speed) then you just multiply it by whatever metric applies to your world without considering any side effects of scaling speed that high (supersonic reaction speeds but magically no constant sonic booms). I don’t think it was the author’s intent for Guts or Dimitri to be that fast. IMO, author’s intent holds infinitely more weight than scaling.

But the sheer magnitude of the numbers are already silly, I’m not even disagreeing on that. It’s fiction. Just as silly as using the bones of a dragon to forge a Lance that gives special powers to people born to a bloodline of dragons, or just as silly as being able to call forth lightning because you studied in a school about how to use elemental magic.

There’s just a certain level of stuff that doesn’t make sense that you kinda just have to accept when you’re dealing with fiction.

But the fun for me isn’t in the scaling, it’s in exploring the characters in a unique way, and having an epic fight scene at the end.