Lydianne Didier, also written as Didieh, is the young daughter of the family that founded Europe's Didier Heavy Industries. Despite being an elementary school student, she possesses PhD-level intelligence and works as a freelance hacker, later taking a part-time position as an exceptional interceptor in the Security Department of the Gigafloat Management Corporation. She presents a youthful appearance with long red hair, often styled in twintails, and purple eyes, and she typically wears a distinctive red uniform reminiscent of a school swimsuit. Her personality is bubbly and childlike, shaped by an obsession with period dramas, yet she is a genius hacker whose skills are recognized by peers like Asagi Aiba, whom she both admires and competes with. Lydianne calls herself Tank Driver and pilots a pink tank into combat. Her role in the story expands significantly when she reveals her affiliation with the organization known as Taishikyoku and takes charge of managing the LYL control program, demonstrating her technical prowess in critical situations. Her motivations revolve around proving her abilities and contributing to the security of the island. Over time, she develops from a freelance hacker into a reliable support figure, working alongside Asagi and Mogwai within the management corporation, and her combination of youthful enthusiasm and expert hacking allows her to handle complex technological threats.