Well, this is fantasy world right? There might be magical seal, stamp or something.
Heck. I read somewhere that banking already exist IRL in middle age with some secret marking or something. Cant confirm this though, and dont bother lmao.
I was dead because i have to save my shitty grandpa who order me to break up with my rich girlfriend, now I was reincarnated with cheat power that allowed me to become popular novelist in another world.
This will be the sequel guys...