A mecha otaku is reincarnated into another world as Ernesti Echevalier (Eru). In this world, exist huge humanoid weapon known as Silhouette Knight. Dreaming of piloting those robots, Eru, with childhood friends, Archid Walter and Adeltrud Walter: together

Mamoru-kun ni Megami no Shukufuku wo! centers around Mamoru Yoshimura, a high school student who gets accepted into a prestigious school for students endowed with the power of Beatrice due to his high intellect. Right after first entering the school on hi