I'm afraid I only know Dipper-san and the Hamada brothers that went. But... I do know that there were deaths. Honestly, Rei, if they weren't acting strange with all that happened there I would be more worried.

As for this Narukami-san, I cannot say I understand their reasoning. Dipper-san is smart, but he's young. He, like so many his age, strive to prove themselves to those they admire, resulting in foolish decisions and actions. He would not have thought through all the consequences, apparently, none of them did.

Or perhaps, they simply do not care if they die, considering they may view themselves immortal.