Robin Sena is a soft-spoken 15-year-old girl with a mysterious origin, given that she has power similar to the witches she helps hunt. She was raised in a convent in Italy before she joined the STN-J. Robin has a fire craft that allow her to manifest varying amounts of fire. In addition, she can channel her energy into shields capable of blocking both solid matter and "crafts", or magical powers, from other craft-users like herself.

However, any use of her power causes her eyesight to weaken—which in turn greatly reduces the accuracy and effectiveness of her pyrokinesis. This problem is easily solved by wearing glasses, but Robin does not like to use them — especially when she first gets them. Though good-natured, Robin has employed her gift to the point of lethal force when necessary to either save someone's life or for the good of others.