The Japanese sure do love to fellate themselves in these Isekai stories. I'd also rather see a small super elite unit like the SAS transported into a hostile world, where they have to at least worry about conserving ammunition and supplies. This Japanese power fantasy quickly gets dull.
"Really effective" my ass... those fan designs are absolutely retarded. There's no air intake anywhere except for the front, where you want your air to be blowing out.
At this point I'm hoping the protagonist forges his own contacts and leaves the retarded father's household. This motherfucker really is too dense to succeed, let his estate fall back into ruin while the MC builds himself an empire.