The point of this whole manga is the dude being so dumb, yet talented at the same time, I suppose like a savant, but it's still annoying that piece of shit yakuza is actually benefitting from it. That being said, realistically a miracle is a miracle because it happens extremely rarely, so what this massage should achieve is the yakuza scumbag forgetting his condition and thus allowing it to develop in peace, until he drops dead. Of course if he visits another place, they might notice and reveal it to him. Is this really going to satisfy like-Kenshiro, who knows. You'd think he would rather have the yakuza die in pain than painlessly.