Ken Matsumura serves as the manager of The Gundam Base, a role that defines his presence throughout Gundam Build Divers Re:RISE. He is an adult male character with blue hair cut to ear length and a visible mustache, often seen wearing an apron while working. His eyes are typically depicted as closed, giving him a calm and observant demeanor.

Within the story, Matsumura acts as a mentor and guide to other characters. He is known for giving lectures on how to build Gunpla, sharing his knowledge and expertise with customers and younger builders. His own fandom is shown through his admiration for Henken Bekkener, a character from Mobile Suit Zeta Gundam, an interest that extends to his GBN avatar being based on that character.

Matsumura has a significant personal connection to the protagonist, Hiroto Kuga. He has known Hiroto since the latter was young, and their relationship is friendly and likely predates the main events of the series. In his professional capacity, Matsumura also interacts with Hinata Mukai when she applies for a job at The Gundam Base. As her manager, he looks out for her and helps her adjust to her new work environment. His role is primarily supportive, providing a familiar and stable presence that connects the characters to the real-world hobby of Gunpla building and the community surrounding it. Information regarding his specific motivations, a defined character arc of development, or notable combat abilities is not available.