[@LokiLeo789] I'm conflicted because this sounds very similar to space-time jutsu and we generally do not accept space-time jutsu because it just create plotholes everywhere. There are exceptions, but this sounds like it's just insane reflex times.

IIRC, Sharingan already has this, too. The eyes move so fast that everything appears in slow motion. Different concept, same premise. 

Furthermore, I can see some hole here in the sense that this sounds like some sort of 'activated' ability. The catch is that byakugan doesn't have, say, 'jutsu' that have to do with the dojutsu (unlike the sharingan, which have a lot of jutsu). A byakugan ability is, when activated, always active. Any application of jutsu afterwards is purely done by the user, and not the dojutsu.

As a result, that would mean that when the user activates their byakugan, they would more or less.. always see in slow motion.

That sounds very annoying to me.

I'm not sure. I'll sleep a night on it, but you can bother Hillan for his opinion.