I've Been Killing Slimes for 300 Years and Maxed Out My Level

Halkara’s new factory has a ghost so she has been unable to hire workers. Azusa summons Beelzebub to help as she is scared of ghosts. Beelzebub forces the ghost to make itself visible, revealing she is a teenage girl called Rosalie who committed suicide centuries ago when her selfish parents sold her to be married to a cruel man. The factory used to be her family home and as a ghost she is trapped in the place she died. Beelzebub reveals if she possesses a human to travel outside the building she will be freed, so Azusa offers Halkara as a convenient vessel, thrilling Rosalie. At Azusa’s home Rosalie realises she is stuck in Halkara’s body, which Beelzebub explains could kill Halkara before long. Attempting to remove Rosalie proves difficult as she can’t be shaken out, exorcised out or even scared out. Hoping putting Rosalie to sleep will help they get her drunk, allowing Halkara to regain her body, then Rosalie is sobered up by dunking Halkara in freezing water, causing Rosalie to jump out of Halkara’s body. Revealing she can use magic Rosalie dispels the rumours about ghosts by making herself useful to the villagers, allowing Halkara to begin hiring workers. (Source: Wikipedia)