Rin and Haruka often mess around with occultic objects and books trying to talk to the dead or summon ghosts. Until they befriend the new girl… Rin and Haruka take it upon themselves to help their strange friend by using their supposed acute knowledge in the occult.
Looks like Rin's ritual didn't go exactly to plan. Right now she's stuck in her dream, trying to figure out how to enter Haruka's dream, if it's even possible.