Saikyou Degarashi Ouji no Anyaku Teii Arasoi

The Adrasia empire on the Vogel continent. There is a battle over the throne of such an empire that possesses powerful military and vast territory. With the successor undecided, the children of the emperor are vying to expand their power. However, there was one prince that everyone says will definitely not become the emperor: the seventh prince, Arnold Lakes Adler. The young man who was inferior to his younger twin brother in every way, the dull prince. Incompetent and lethargic, Arnold wastes everyday just playing around. However, behind the scenes, he is one of the only five SS-Class adventurers called "Silver." Seeing the intensifying battle for the throne he decided "I don't want to die, so let's have my little brother become the emperor…" This is the tale of absurd secret maneuvers of the prince who is uninterested in the title of the emperor.

(Source: Shousetsuka ni Narou, translated)