I just realized I should clarify a few things regarding Enma.

So, yes, normally holy objects can harm him (They can't kill him, since he's immortal, but they can drive him off or severely weaken him). However, there is a catch. The first thing is that it doesn't matter what culture/belief/etc. the object originated from. All that matter is that it's a holy object related to said culture/belief/etc. Second, it's not necessary to actually believe in anything supernatural/holy. The main thing that matters is whether or not the person wielding it is someone who is genuinely heroic/good/noble. That being said, being both heroic and believing in the supernatural/holy does make holy objects more effective against Enma (Though, Enma is more of a neutral force than outright evil in this case).