Aoi is a clone produced using Kurei's and Kurenai's genes. Due to his inability to generate flames, he is deemed a failure and feels incredibly jealous towards the only 'successful' clone, Renge. He wields a gun, but his true strength lies in the madōgu, Shinryo Shikō, which enables him to alter one's memory. He also wields a sword attached to his right hand, but it is unknown if this is an unnamed madogu, or simply a basic weapon.
Part in Story
Sealed Lands arc
He first appears in the Sealed Lands, where he easily defeated an injured Tokiya Mikagami after the latter emerged victorious against Mokuren and Mikoto. After Rasen loses the will to fight, Aoi replaces him as the leader of the Ura Uruha.
He eventually transfers to Nashikiri High School in order to befriend Yanagi and the others. This is because his mission was to kidnap Yanagi and erase her memory so that she could be 'absorbed' by the Tendō Jigoku, and the Shinryo Shikō can only tamper with the memories that both the target and the user are aware of. Yanagi's kindness to him makes him doubt his loyalty to Mori.
He is defeated by Recca, wherein he is actually found out to be a boy not a girl and he defects from the Ura Uruha to join the Hokage to destroy Tendō Jigoku. After Tendō Jigoku is destroyed, he stays at Domon's house and helps out at the Ishijima Flower Shop.
Shinryo Shikō (神慮思考, Divine Thought): An armband endowed with three crystal spheres. It allows the user to alter memories, given that he or she knows the memories to be altered. It can only keep a certain amount of memories altered, regardless on how many people it was used on. So in order to use the Shinryo Shikō on a new memory, some of the old memories it altered might need to be returned to their previous states.
He also has an unnamed madōgu that takes the form of a collapsible arm-blade. The base of the blade is capable of splitting into prongs for defensive use.
Also, unlike most of the characters that use madōgu, he also uses a gun.