The restorer of ancient books, Yu Ziran, is probably the dullest being in the three realms - she can understand the writing of the underworld, but she regards Yin difference as a cosplayer; she has a constitution that can purify Yin energy, but she is completely unaware of the black mist that surrounds her. Until one day, she used glue to repair a bleeding "thread-bound book", which actually opened a hole between the Yin and Yang worlds.
Intention: Go both ways