David Krueger, also known as Darbit Kruegel, serves as Tekkaman Sommer within the Space Knights. He survived the Black September incident in Prague, a nuclear attack that obliterated the city following a Tekkaman cult uprising. Rescued moments before detonation by Aki Kisaragi, then operating as the Red Devil, David witnessed the deaths of his friends and family during the evacuation. This event left him with profound survivor's guilt and psychological trauma, leading him to frequent bars to drown his sorrows behind an outwardly easygoing, joke-telling facade.

As a "Primary Body" Tekkaman—a human who began but did not complete the Radam transformation—David required Earth-engineered biotechnology to achieve his full Tekkaman Sommer form. He wields twin Voltekka cannons mounted on his shoulders and uses a lance as his primary weapon. He operates within a new Space Knights trio alongside Natasha Pablochiva (Tekkaman Vesna) and Yumi Francois (Tekkaman Hiver).

David harbors unrequited feelings for Aki, his rescuer during Black September, though he recognizes her longstanding romantic connection to Takaya Aiba (D-Boy/Tekkaman Blade). This unattainable affection compounds his emotional struggles. His character arc intensifies through his bond with Dead End, another survivor of Prague's destruction. They connect over mutual loss, meeting first in a graveyard and later in bars. David sees Dead End as the only person who understands his trauma, unaware initially that Dead End is a rogue Tekkaman driven by vengeance against Aki, whom he blames for the Prague tragedy.

David's psychological state deteriorates as Dead End escalates attacks against the Space Knights, specifically targeting Blade. During their third encounter, David discovers Dead End's Tek crystal, revealing his identity. This forces David to confront the conflict between their shared trauma and Dead End's destructive path. In the climax, David witnesses Blade's final battle against Dead End, though his personal resolution remains ambiguous.