Otogi Sekai no Oosuke

About this title

Oosuke, a high school student, had promised to illustrate a children's story written by his childhood friend Izumi. When Izumi's story wins a prize and the time is finally right, she is attacked by an unworldly creature...? The girl creates the story, and the boy moves it! A battle fantasy of fairy tales! (Shonen Jump Plus, translated)