Yorishiro

A divine yorishiro (依代) is the most precious possession of a school mystery.

The yorishiro acts as a battery that provides the school mystery with power and is kept in the innermost reaches of a school mystery's boundary.

It has a black seal on it and will cause the school mystery to cease function if it is taken off.

In volume 3, Hanako explains that there is a traitor in between the 7 mysteries who is changing the rumors. He then has the idea to simply erase the 7 mysteries for a while by destroying their yorishiro before they go out of control.

After Nene rips the seal off a yorishiro, she will drift to sleep and see a part of the past memory that was connected to the item.

Yako's yorishiro is a pair of scissors, presumably the one used by Misaki to cut hair as written in the journal.

After taking away the seal from Yako's yorishiro, a memory of the past was shown. The memory was of the teacher, Misaki, taking a picture in front of the temple along with the fox statue beside the gate.

Misaki told everyone to look forward and smile, then patted the statue and said "You too". The fox statue was Yako.

Tsuchigomori's yorishiro was a 'lunar rock' that is connected to the only person he has ever seen who managed to change the future from how it was written in the books, Yugi Amane, Hanako's past self. After taking away the seal from Tsuchigomori's yorishiro, a memory of the past was shown. The memory was of Yugi Amane, who was being bandaged by him from many injuries and bruises. Amane then talks about a rock he owned that fell from the sky and claimed for it to be a lunar rock. Amane described the rock as his 'prize possession'. He then gave it to Tsuchigomori, despite saying that the rock made him felt like he could go anywhere. Amane then said "I've made up my mind now, I'm not going anywhere." and had a different future from what was written in the books, something that Tsuchigomori had never seen happen before.

No. 3's Yorishiro is placed on the ceiling of his mirror world. Nene and Mitsuba were supposed to take the yorishiro off in order to get out of the mirror world, however they couldn't thanks to Tsukasa's intervention, which cuts the no. 3 into pieces. The Yorishiro isn't mentioned anymore after Tsukasa kills No. 3 and feeds his heart to Mitsuba. It is unclear whether the current No.3 still have the same Yorishiro or not, as it doesn't seem to have any correlation in transferring powers.

Shijima Mei's yorishiro is a sketchbook, the same one the original Mei used to sketch the Tower. After taking away the seal from Shijima Mei's yorishiro, the Picture Perfect world shatters into glass, showing glimpses of their experiences in the fake world. The sketchbook is burned into nothingness. The fabricated world ceases to exist.