Inukai Shinji is one grade below the main character and another guardian. Shinji has the power of creating shields and can use the power of words to control anything and anyone by giving the words special meanings. Despite his looks, he is very strong-willed and stubborn.
He likes cooking & is good at it. He is very gentle and enjoys being around his friends to the point where he thinks that by having Onikirimaru removed from the village, his friends and him could live in peace, which made him into the traitor. It has been shown that he has special feelings towards Mitsuru and was deeply hurt to discover that they were twins.
Despite not being the true guardian of the Inukai family, Shinji possess the ability of fast recovery most likely due to the fact of having Monado Aria awake his powers. Although not being born a guardian, Shinji awakened as a guardian of Princess Tamayori and has the power of creating shield and can use specialized words to control objects in his surroundings.