万能スキルの劣等聖女 ～器用すぎるので貧乏にはなりませんでした～

In a world where crests grant powers that decide one's fate, Prince Heale is born with Cave King—a crest just as obscure and useless as he is. Deemed a disgrace to his family, he's exiled to a barren, deserted island without a single living thing in sight. Alone and miserable but determined to survive, he reaches for a pickax to expand the cave he takes shelter in—and uncovers the true power of his crest! It turns out Cave King makes mining and building within caves as easy as breathing. Useless no more! Instead of a life in limbo waiting for rescue, what Heale finds on this island are otherworldly discoveries and life-changing encounters! (Source: J-Novel Club)