Mitsunari Miyazawa is a high school student who aspires to become a writer. Suddenly, in a battle he gets involved in, a demon takes his life, and Mitsunari awakens to the power of the "jealousy" mage and is revived. Together with his partner, the grimoire Lydia, Mitsunari's life as a grimoire begins now--!

Translated via DeepL so this description could change in the future.