Tata no Mahou Tsukai

One day, a witch appears in a Japanese high school and grants the wishes the students wrote in their middle school graduation book. This results in the entire grade being transported to a fantasy world because of somebody's wish to “escape” the world. As the students come to terms with the wishes they made, they have to fight to survive in a dangerous world completely unlike their own. The book is written like a documentary, following the story of hundreds of students instead of a single protagonist. Grand Prize winner of the 24th Dengeki Novel Prize.

(Source: Anime News Network)