The Insipid Prince's Furtive Grab for the Throne

Saikyou Degarashi Ouji no Anyaku Teii Arasoi: Munou wo Enjiru SS Rank Ouji wa Koui Keishou-sen wo Kage kara Shihai suru · 最強出涸らし皇子の暗躍帝位争い 無能を演じるSSランク皇子は皇位継承戦を影から支配する

To the empire, Prince Arnold is one big joke, a completely inept prince outshone by his more talented twin, Leonard. But in secret, Arnold operates as Silver, one of only five magic-wielding SS-rank adventurers on the continent. As the bloody battle for the throne intensifies after the crown prince’s death, Arnold pulls the strings from the shadows to crown his twin emperor to his own advantage. (Source: Crunchyroll)