Originally Posted by
ItsaRandomUsername
The barrier around Ryuudouji no-sells spirits wanting to take a shortcut, so yeah, basically. No comment on the exactitude of the mystery behind it, but I'm sure that on the napkin buried in his underwear drawer that Nasu wrote the notes for the nixed Issei route on would've expanded upon those juicy lore bits.- - - Updated - - -Mystery AND fueled with magic to deliver the goods. Bopping someone with a famous old rock probably isn't enough to do the trick, although I'm sure someone could write a scenario where there's an exception.