Otogibanashi wa Jigoku no Hate,

Overview

There are four Magic Divisions in the military giant that is the Kingdom of Hiraith. The First Magic Division is the elite of the royal guard, the Second Magic Division is the field combat unit, the Third Magic Division is the research and development organization for magic and magical tools, and the Fourth Magic Division consists of those who have other unique skillsets. Among them, Levi was the most unusual, being a sorcerer incapable of using magic and having nothing he wanted to accomplish. In the midst of his days of mere subsistence and despair, Levi meets Prince Saphir, the 13th prince, who is known as the Moribund Prince. Levi, 16 years old, and 6-year-old Saphir...it was a fateful encounter! In a royal palace full of malice, the two of them discover human warmth for the first time... (Source: Taiyo Tosho, translated)

Source: AniList