Mugen no Majutsushi - Maryoku Nashi de Heimin no Ko to Hakugaisareta Ore. Jitsu wa Mugen no Maryokumochi

Resto, a boy who was reincarnated with unlimited magical power. For some reason, he pretends to have no magic power and spends his days enduring persecution, but... But his life changes forever when he saves the lives of Viola and Primula, the daughters of a court magician! To have as many children as possible of his blood born to the Marquise Rosemary... Recognized as a gifted magician and his sisters' son-in-law, Resto spends his days training for the entrance exam to the Royal Academy as a live-in student... His talent is honed as he defeats unorthodox demons and develops unorthodox magic, accomplishing feats no one could have predicted. ___ Winner of the 9th Kakuyom Web Novel Contest, Otherworldly Fantasy Category Special Award & CW Manga Award.