Cerberus Jam

Cerberus Jam (ケルベロスジャム, Kerberos Jam) is a manga written and illustrated by Haruto Shiota. It was serialized in GFantasy from September 17, 2011 to December 17, 2011

Plot
Seri, a somewhat directionally challenged girl, went to Umeda for a job interview. Finding herself completely lost, she stumbles across a slightly opened door and decides to try her luck. She takes the stairs behind the door, emerging on a peculiar street half an hour later. Unknown to Seri, she has just mistakenly entered a place far more dangerous than she could ever imagine.