Tetsu Sabi to 1000 Carat

This is a world where "Jewel-sama" are born with jewels in their eyes and special abilities. They live in a vast mansion called the "Jewel Box," and their duty is to grant people's wishes. The new arrival at the Jewel Box is Yuni, a girl with iron ore in her eyes, who is far from a beautiful jewel. Although she started her life as a "Master Jewel," she was not able to help people as much as she would like. Then she meets Alecrea, a master jeweler who is rumored to be a "Jewel Killer." He seems to be pursuing the unknown dark side of the jewelry box. In order to get closer to the truth, Yuni helps Alecrea and meets various other jewelry masters. Little does she know that she herself will eventually become the one to change the world. Follow your wishes and uncover the truth of the beautiful jewel box world. The unpredictable buddy and love fantasy between a girl with black iron and a rebellious young man begins! (Source: Pixiv Sylph, translated)