"Mental defenses, at least, would affect a ghost capable of coherent thought," replied Toshiko, approached Ryuuko as her apprentice made a beeline for something on the wall. Ghosts were beings with human thought patterns, and as a result spells designed to effect those thought patterns would still effect them. Even if they didn't set off the more physical defenses, the ones targeting the mind would still be able to detect them. When Ryuuko discovered that scrap of paper, however...

"You're certainly right, Ryuuko-kun," she commented, eyes travelling over the piece of paper. There was no denying what it appeared to be, it was definitely a piece of ofuda. That was only something that an onmyouji would use.

Yuuno stared for a few moments.

"Ehhh? There's... we never use ofuda!" the smallish girl exclaimed, "That's not how a proper magi does magic!"

As Toshiko glanced down the wall, she noticed spots on the wall that seemed slightly... scuffed? As if something had been attached to them...

"... Oi, Yuuno-chan," Toshiko said, turning towards the girl, "Is there any way that these spells could be disrupted without direct magical interference?"

Yuuno paused for a moment, looking thoughtful. "... I guess if the pattern was interrupted, but that's tied to the walls, and the walls are still there..."