I disagree, it was always implied that kaijus have been around since forever, and we already knew about this one appearing in the samurai era, so I don't know why you're so impressed now
im sure you know exactly which chapter mentions exactly when kaijus appeared... somehow
i know about this "armor" that has been appearing before Kafka several times, now we know its probably a manifestation of previous "users" of number #8 and that the Hoshina family has a history slaying monsters for the goverment, that doesnt exactly explain HOW humanity has survived, one swing of an arm from this monster, which we can assume is just riffraff, and everyone is dead
just imagine a monster on the tier of the numbers
its just... such a surface level plotpoint its boring, and the more you think about it, the worst it gets
but hey, they can always remedy it, it just felt like it was meant to be this amazing reveal and im just like "okay?"
i was already struggling keeping interest after Mina being eaten for 5 months, or this number #9 fight that feels like it has been going on for 2 years, im kinda just done, but you do you if you enjoy it