Whether at the office or at home, corporate drone Yuji Sano works all the time. So when his home PC flashes a message about him being summoned to another world, Yuji restarts his machine…only to find that he’s inadvertently accepted the summons! Now in a fantasy world far removed from paperwork and computers, Yuji has just one thing on his mind: waking up from what he thinks is a dream and getting back to the mountain of work he left behind! But this other world has other plans for Yuji, who quickly discovers his Monster Tamer character class allows him to befriend slimes! And thanks to their number, those slimes help him absorb so much magical knowledge that he gains a second character class in the blink of an eye! How will Yuji wield his power now that he’s the greatest sage the realm has ever known?! And what about all that paperwork?!

Surrounded by a forest and a gated entrance, the Grace Field House is inhabited by orphans happily living together as one big family, looked after by their "Mama," Isabella. Although they are required to take tests daily, the children are free to spend their time as they see fit, usually playing outside, as long as they do not venture too far from the orphanage — a rule they are expected to follow no matter what. However, all good times must come to an end, as every few months, a child is adopted and sent to live with their new family... never to be heard from again. However, the three oldest siblings have their suspicions about what is actually happening at the orphanage, and they are about to discover the cruel fate that awaits the children living at Grace Field, including the twisted nature of their beloved Mama.