Martin Tachibana, an American-Japanese scientist and Valencia's father, operates as a renegade researcher in San Francisco. He develops biotechnology to artificially create "Neo-Aragami," bypassing the god Susanoo's power. These experiments unleash a new wave of monster attacks across California, forcing the U.S. government to reactivate the Terrestrial Administration Center (TAC) team.

His scientific work directly leads to his daughter, Valencia Tachibana, being implanted with an Aragami soul (mitama). This condition prevents her full transformation into an Aragami, mirroring Mamoru Kusanagi's situation. Martin Tachibana's role is confined to instigating this Neo-Aragami crisis within the Blue Seed Beyond OVA narrative. He is abruptly defeated during the OVA's conclusion.