I remember at the end of OT where Hamazura about to torture that helmet girl and he hides it from Takitsubo and Mugino because he doesn't want them to see it.
Only for Mugino in this chapter "Well shit man, I did a lot worse than that".
York: So when can I become Celestial Dragon? :meguu:
Garling: Pffft haha nice joke :lol::lol: As a subordinate you know how to ease it up with your boss. Now get to work. Also we have food shortage right now so you'll be eating scraps.
York: :meguuusad:
Conclusion: Richard J. Gatling got isekai'd into this world, popularizes the concept of Gatling, then went back to his world and continue his life like history suggest.
Other detectives solves case after the crime has happened.
Akane solved the case before the crime happened thus preventing the loss of life.
That's why she is the best.