Mugen no Majutsushi: Maryoku Nashi de Heimin no Ko to Hakugai sareta Ore. Jitsu wa Mugen no Maryokumochi.

Lesst, born between a noble and a commoner, is deemed to have “no magical power” during his magic aptitude test. In reality, however, he possesses an infinite amount of magical power. Treated as a commoner and persecuted by his older brothers, Lesst resolves to become a court mage in order to prove his worth and show them what he is truly capable of. Then, after a fateful incident, he catches the attention of the daughters of court mages, and his grand rise from the bottom begins. (Source: ComicWalker, translated)