Starting an RPG with the Demonlord

A string of mysterious disappearances has been making headlines. Rumor has it that all the missing people have been "reincarnated into another world." Yoshimichi, the protagonist, dismisses the gossip as nonsense until one day, even his childhood friend, Yuma, suddenly vanishes without a trace. His classmate Otogi insists that Yuuma's disappearance must be an isekai reincarnation and excitedly declares that she wants to go to another world too! Before Yoshimichi can stop her, she drags him into a suspicious building...!?