I think the webtoon adaptation decided not to include the "shenanigans" of the japanese hunter association in the LN mainly because it might create a friction to their japanese readers. I am okay with this though, shows that they are giving respect to their fellow asians. Believe it or not, there are small tension already between the Japanese and the Koreans, so including that LN part would not be wise, and it doesn't really affect the outcome of this arc all that much.