"I'll create a witch!!"

During the 17th century, the German alchemist Johann Schultz successfully created a witch. He then injected that power into his own blood. In the present day, as a result of a scheme created by his cousin, Yomoda Rena, Shurutsu Kenichi, a high school student and a third generation German, fights on secretly as a blood relative of "Brocken", all in order to hunt down those who abuse the artificial witch theorem. Yet for reasons unknown, he transforms into a Magical Girl "Heroine"...?