Aren Kuboyasu was a delinquent while he was at his former school, which only Kusuo, Shun, Mikoto and Touma know. Like a typical delinquent, aside from being strong and being called in fights, Aren is short-tempered when someone is being rude to him. He had a hard time controlling his temper when he first moved to PK Academy. He also has a tendency to grab anything near him and throw it at the person he's angry at (he nearly killed Takahashi just because they brushed shoulders). Aren also sometimes makes an evil, devilish face when he's angry with someone or is opposing someone, which scares them. However, he acts naive and childish when the talk is about motorbikes.