Light Novel Volume 3

The strongest dull prince's battle for the throne, The SS rank prince who acts incompetent will control the succession war from the shadows 3(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 3lit. Saikyō degarashi ōji no an'yaku teii arasoi munō o enjiru SS ranku ōji wa kōi keishō-sen o kage kara shihai suru 3) is the third light novel of the series and was published on May 1, 2020.

Summary
Even whilst overseas, the incompetent prince Arnold maneuvered behind the scenes and successfully raised his brother, Leonard's reputation. His relief is short lived, as the emperor tasks him with the dealing of a marriage proposal to the strongest general of the Imperial family, the first princess, Lizelotte. Meanwhile, Leonard was tasked with alleviating the troubles plaguing the migrant village. However, during the investigation an abnormal incident which threatens to shake the empire to the core occurs!?

With the looming crisis facing the empire and its subjects, the tenacious Leo dashes head in. Al, who witnessed that growth and resolve ―― "The future emperor told me to show my full power. It won't be nice if I don't reply in kind." To save his younger brother and protect the empire, the dull prince will carry out secret maneuvers even on the battlefield!