Wataru Shijima (四十万 ワタルShijima Wataru?)/Baron the Thunder Knight (雷鳴騎士・破狼（バロン）Raimei Kishi Baron?, [Note 5]) is a Makai Knight serving the Senate, donning a suit of azure armor similar in style to Bado's and wields the Raimeiken (雷鳴剣?, Thunder Sword) like a scimitar in his armored form. In charge of training the young Makai Knights-to-be, Wataru gains infamy for his draconian methods. He considers the bloodline of a student's Makai Knight family to be of no importance, unless the person-in-question has the strength to protect others, and that one should try his or her best even though chances might be slim. Wataru happened to have Kouga under his tutelage while a boy, playing a vital role in helping to foster the youth into who he is now. Sent on a mission to find the red-masked man, Wataru is ambushed by the villain as he marks him with the seal of destruction, causing his inner darkness to awaken. Being almost completely taken over by his dark side, Wataru is forced to attack his fellow Makai Knights as he attempts to keep himself at bay. He tried to kill himself to avoid being taken over completely by the darkness within him, only to be stopped by his evil side. Eventually, Kouga and Tsubasa manage to purge the evil influence from his armor and returning him to normal. While telling Kouga of the possible tension between the knights and the priests that can be caused by the Sigma Fudō's actions, Wataru recognizes him as his pupil.
Wataru Shijima is portrayed by Kenji Matsuda (松田 賢二Matsuda Kenji?), known for his roles in Kamen Rider Hibiki and Kamen Rider Kiva.