Ryota's original weapon, which happens to get broken in weapon form, which results in the spirit being unable to fight in Heavenly Armament form. However, she tags along with Ryota regardless as his friend. Shes usually excited and bubbly, and does her best to encourage Ryota, cheer him on, and congradulate him on his victories, but also can get intimidated rather easily in the face of danger, probably because shes already suffered enough damage. Although she had a different name, after waking up from being damaged, she asks Ryota for something to call her as a name. Seeing that no other weapon in the academy would be like her, Ryota decides to call her Yui. (which one of its many meanings is only, unique, etc)