Knights & Magic
A mecha otaku is reincarnated into another world as Ernesti "Eru" Echevalier. In this magical world, the country is protected by knights who pilot a kind of large humanoid weapon known as the Silhouette Knights. Dreaming of piloting these robots, Eru and his childhood friends, Archid and Adeltrud Olter, study Magic and work toward their goal together.
The manga adaptation of the light novel series by the same name.