Achievement
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Fortunate
Miroku has had an interesting day, for all the many near-death experiences. The best bit was actually waking up again despite having sucked all those Saimyousho into his wind tunnel. Sango begging to stay by his side even to the death was very nice too, though.
His survival led him to deduce they were on ground so holy the insects' poison in his body was being purified, which was the kind of stupidly good luck Kagome usually got. Wandering around with her for so long had clearly caused some of the luck to rub off, which was the strangest advantage he'd ever thought of getting from her company.
Saint
After realising they weren't going to die just yet monk and demon slayer followed the tunnel to a temple in the heart of the mountain, where Miroku recognises the mummified -yet still living- body of Hakushin. Miroku, disgruntled that a saint is is offering assistance to a being as blatently evil as Naraku, demands that the holy man explain himself.
Sinner
The saint explains that he resented those who expected him to die willingly to save their lives. Miroku doesn't bother to argue the point -Hakushin's objection is reasonable- but tries nonetheless to break down the barrier around the mountain. Hitting it with his staff doesn't work and neither does Sango's Hiraikotsu. In the end the monk decides he can't afford to play around any longer when the world and his friends are at stake and uncovers his wind tunnel, sucking the barrier into the void.
Then both monk and demon slayer hear the howling of many, many youkai that are no longer being kept away from them.
Miroku and Sango break the barrier. Oops.