Benkei Kuruma stands central to the narrative, sharing a deep, longstanding friendship with Musashi Tomoe rooted in their shared Japanese military service. He served as Musashi's Junior Major following the original Getter Team's dissolution. After an incident involving Dr. Saotome's apparent death, Benkei maintained silence at Musashi's request to protect the doctor's younger daughter, Genki, from further trauma. During ensuing conflicts, he aided the injured medically and later sought refuge underground with the amnesiac Genki. Renaming her Kei to distance her from her past, Benkei became her guardian while simultaneously mentoring a young engineer named Gai.

Thirteen years after a global catastrophe triggered by a nuclear strike on the Shin Dragon, Benkei emerged from hiding to support Kei during battles against Hayato Jin's mobile fortress, the Tower. Following the severe damage inflicted on the Shin Getter and Black Getter robots by Shin Dragon, Benkei recovered from his injuries and joined Ryoma Nagare and Hayato Jin as the third pilot within the Shin Getter to combat the extraterrestrial Invaders.

Fundamentally compassionate and prioritizing others' well-being, Benkei dedicated himself to protecting and guiding Kei and Gai after Musashi's death. Within the reformed Getter Team, he strove to mediate the strained dynamic between Ryoma and Hayato, attempting to emulate Musashi's example, though his own unresolved doubts initially hindered these efforts. A pivotal encounter with Musashi's spirit spurred Benkei to persevere in safeguarding Kei and commit fully to the mission of eliminating the Invaders, solidifying his resolve.

The conflict culminated in a final battle against the Invaders in outer space. Benkei, alongside Ryoma and Hayato, executed the sacrificial Shin Shine Spark attack to ensure the enemy's defeat. This act transported them to Getter Valhalla, a dimension where they engage in perpetual combat alongside other incarnations of themselves.