I wouldn't overestimate the fan as a weapon. Even when made out of steel it cant weight too much (or it would seem very sus during any sort of weapons-check), and due to short length the energy transfer wouldn't be that efficient.
Still, better than nothing, and definitely very stylish.
Something I dont get is why is MC surprised at all... He's been living in this world for years now, and studying its laws and customs. Why does he still act like he reincarnated yesterday?
Guys, you really need a proofreader for this. And if you have one, well, I'm sorry but he needs to step up his game. 9 pages into the chapter and there's already several big mistakes. (and that's not even new translation, since that part was released before!)