Otherside Picnic Vol 1

Otherside Picnic by Iori Miyazawa. A Yuri manga rated Older Teen, published in English by Square Enix.

College student Sorawo Kamikoshi discovers a way into the Otherside, an eerie parallel world where urban legends and internet horror stories come to life. There she meets Toriko, a striking woman searching for a missing friend, and the two begin exploring the Otherside together.