Yomei Hantoshi to Senkoku Sareta node, Shinuki de "Hikari Mahou" wo Oboete Noroi wo Hodokou to Omoimasu. Noroware Ouji no Yari Naoshi

Prince Callus Leditzweissen is a Taboo Being, an unfortunate soul born with a deadly curse that causes him constant suffering. With no known cure, the doctors say Callus only has six months left to live. But a magician named Gourley gives the boy a sliver of hope when he demonstrates the healing power of light magic. Callus is determined to learn how to use light magic in time to save himself, hoping to live longer to repay all the kindness he's been shown throughout his life. (Source: J-Novel Club)