I shot the Devil - but I did not shoot the host body
(And yes please do read that to the tune of "I shot the sheriff") Lately, a couple of very interesting guns have been introduced in Ao no Exorcist. First, we had the Armumahel gunslinger set...
And then in chapter 112 we were introduced to this fabulously named invention:
Interestingly, both weapons target only the SPIRIT, and NOT the host body.
Now, the most obvious conclusion is that Lucifer intends to use his guns against Samael, and Samael intends to use his gun against Lucifer or Satan, or both. But.
Neuhaus reveals some really interesting things about Mephisto's Kinky Gun:
...Did y'all notice that just now? Made in the last 15 years. Human identity binds to things more strongly than demons can.
Yukio is flame-resistant, including Yamantaka's & Rin's. Not only would he be able wield both the Armumahel guns and the Devil * Punisher without problem, but he could do so while withstanding a first rate devil tantrum (if we can believe Egyn, that is- but going by what we've seen of Blue Night so far, Yukio has probably always been a pretty fireproof baby).
And previously, I theorized that Mephisto never intended for Rin to fight with his body, as Rin's control over his demonic self and his satanic abilities have nothing to do with physical, but with mental strength- and that Mephisto might have intended to give the twins as host bodies to Satan & Lucifer respectively, once he could be sure that they wouldn't budge to the force that tries to overtake them.... So that the demons would effectively be locked up inside them by sheer force of will, similar to how Shiro managed to fight off possession by Satan for years. Add up to that the fact that Shiro seemed to know Satan would come for Rin, the fact that this gun has been in development since the twins were born, and the fact that Mephisto is a time-looping mastermind...
...And Rin might be getting some brotherly assistance in yeeting the Devil out of him entirely~