I'm just gonna go on a bit of a confused rant here hoping someone can help clear this up.

After Amaterasu gives Kushi a ride to the Moon Cave entrance, they bump into Waka, who uses the Serpent Crystal, his awesome flute, and his katana to dispel the barrier at the Moon Cave, something that only he can do, apparently. But when Orochi nabs Kushi and retreats into the cave, this next bit is what I don't understand.

Amaterasu follows suit with Issun, but the barrier magically returns, trapping the two of them inside. Issun for some reason, immediately singles out Waka. But Waka himself mentions that "only one other than the victim may get in". So, doesn't that mean that after Ammy enters, no one else is really supposed to be able to go in? Why does Issun make it sound like Waka pulled a dick move and purposely trapped them in the Moon Cave? I don't get it...was Waka to blame or not?