It's simple, Sophie wants her ass sniffed and the slaves balls will pay dearly if he doesn't sniff it correctly. With his face under her ass and his nose deep in her ass crack, the slave inhales her ass fumes deeply and repeatedly as best he can. But apparently not well enough. Sophie seems a bit irate today and takes it out on his balls, slapping them hard sometimes for no reason at all. Oh well, looks like the slave will not be able to escape ball today no matter how much he smells her ass.