Aoba is 1st year student in Raira Academy. He has a bright personality and is always seen smiling, but has also a darker side to him. He's described as being akin to "a younger version of Orihara Izaya".
When he was in elementary school his older brother Izumii Ran physically abused him, so Aoba in revenge set out fire in Ran's bedroom and Ran took the blame, as the adults thought the fire started from his cigarette. After their parents' divorce, Aoba went to live with his mother and changed his surname from Izumii to Kuronuma. A few years later, he formed Blue Square and ceded its leadership to Ran.
