Mahou Tsukai Kurohime 1-18

A young boy is saved by a mysterious gunfighter who uses magical bullets. She is the greatest magician in the world but disappears shortly after saving him. Having fallen in love with her, he trains to become a gun fighter and ten years later, his search comes to an end but his adventure has just begun. Kurohime is a buxom witch with the power to control magical guns. She once made the mistake of challenging the gods and was cursed for her foolishness! Transformed into a little girl named Himeko, she can only regain her former body and powers when she falls in love. But finding love in a world fraught with evil is no easy task.