"I Had School Refusal, But I Gathered My Courage and Went to School, Only to Have My Entire Class Transported to Another World ~ The Avenger of the Forbidden Grimoire ~"

For several months, Katari had been refusing to go to school and shut himself away at home. However, persuaded by his childhood friend, he decides to return to school. But what awaited him was brutal bullying. Katari swears revenge against his classmates and puts a knife in his bag before heading to school again. Just as he's about to cause mayhem, for some reason he gets caught up in a transfer to another world. Katari obtains a grimoire filled only with unethical forbidden magic, and devises a plan to slaughter all of his classmates.