Rokurouta Sakuragi (桜木 六郎太 Sakuragi Rokurouta) (voiced by: Rikiya Koyama), aged eighteen, and referred as 'An-chan' (bro) by his cell-mates, is the oldest of the seven protagonists in Rainbow. He is a strong and benevolent young man who is treasured by his friends and is considered to be a role model to them. He also has great boxing technique, which he demonstrated by knocking out all six newcomers when Mario started a fight. He constantly looks out for the well-being of his cell-mates. This often means sacrificing himself for them, making him the routine victim of Ishihara's schemes. He is the only boy at the prison who does not fear Ishihara.
Sakuragi is a tall, handsome young man. He has dark brown hair and light brown pointed eyes. He is also very muscular.
When he was younger, his father and five brothers went off to war. Only his father survived, returning home a broken man and a drunk. Sakuragi's father later committed suicide after arguing with Sakuragi one night, leaving Sakuragi racked with guilt. As a result of this, Sakuragi resolves to never lose anyone else important to him. His friend and former cell mate, Hagino, was violated by Dr. Sasaki. Before committing suicide because of the rape, Hagino wrote a suicidal note which blames the two of them, giving Sakuragi evidence of Ishihara's and Dr. Sasaki's crimes. Due to this, Ishihara and Dr. Sasaki both want him dead. After being stabbed by Ishihara, he goes to see Mario's boxing match, but is shot down by American soldiers on his way there.
Sakuragi was in love with Setsuko and wanted eventually to marry her. They fell in love when Sakuragi was treated at the Hospital for the first time due to deadly damage to his body.