Mayuko Hasekura is a member of the development team within Under Anchor, the secret organization that creates and maintains the Phone Bravers. She is consistently described as a very cheerful and upbeat young woman, and her primary role is technical support: she helps keep the Phone Bravers in good working order, handling maintenance and repairs alongside the rest of the development staff. Her bright and positive disposition makes her a pleasant presence in the Under Anchor facility, contributing to the team's morale. While she does not engage directly in field missions, her work behind the scenes is essential to the operations of the Phone Bravers and their human buddies. She works closely with the head of the development team, Kohei Mito, and other tech specialists such as Mutsuki Sakaki and Hirofumi Morishita. Mayuko does not undergo a dramatic character arc over the course of the series; her core personality remains consistently supportive and industrious. Her notable ability lies in her technical expertise with the Phone Bravers’ hardware and software, ensuring they are ready for action. She has no supernatural or combat abilities, but her reliability and good-natured teamwork make her a valued asset to Under Anchor.