Kōhei Mito is the head of the development team for Under Anchor, the secret organization that created and maintains the Phone Bravers. He is responsible for repairing the damaged Phone Braver units and oversees the technical side of the organization's operations. Mito is often referred to affectionately by his colleagues as Goinkyo, a nickname that means retired person, reflecting his status as an older, experienced figure who is respected for his wisdom and long service. He has a calm and approachable demeanor, and his colleagues view him as a mentor and a source of steady guidance.

Mito played a key role in the origins of the Phone Braver project. He was the person who brought together Yuto Date and Masayoshi Soda, the two individuals whose combined expertise in robotics and artificial intelligence made the Phone Bravers possible. Mito's own inspiration for the concept came from a girl named Yuuri, which gave the project a deeply personal and emotional foundation. His motivations are rooted in a desire to create technology that can protect people and foster meaningful connections.

Within the story, Mito serves as a behind-the-scenes support figure. He is not a field agent but instead provides the technical backbone that allows the Phone Bravers and their human buddies to function effectively. He also designed and implemented the training exercise known as The Last Day on Earth, an elaborate simulation that tests new agents by simulating an alien invasion, pushing them to their limits to prepare them for real missions. This shows his dedication to ensuring agents are fully capable before entering the field.

Mito has a friendly relationship with the members of Under Anchor, particularly with the development team, which includes Mayuko Hasekura, Hirofumi Morishita, and others. He treats the younger members with patience and encourages their growth. His connection to the wider Anchor organization is significant, as he was instrumental in forming the alliance between Date and Soda that led to the creation of the Phone Bravers. He also has a lighthearted side, being a known fan of the singer Hitomi Shimatani, which adds a humanizing touch to his character.

Over the course of the series, Mito remains a constant presence in the background, providing repairs, upgrades, and strategic advice. He does not undergo dramatic personal development himself, but his steady reliability and technical expertise are crucial to the success of Under Anchor's missions. His notable abilities lie in his engineering and programming skills, his understanding of the Phone Bravers' inner workings, and his capacity to design effective training programs. He is not a combatant, but his contributions are indispensable.