Don Genosai is the primary antagonist of the VS Knight Lamune & 40 Fire narrative. As head priest of the Kira Kira temple, he orchestrates efforts to resurrect the demon god Abraham, triggering dimensional collisions that endanger multiple worlds. He commands subordinate antagonists Narcist Dandy and Pheromone Lip, directing missions like the kidnappings of Arara kingdom residents Lesqua and Cocoa for enslavement.

Genosai employs direct manipulation of allies and enemies. He successfully brainwashes Cocoa and Lesqua, transforming them into dominatrix-style assassins wielding lightsabers to ambush protagonists Lamunade and Da Cider, demonstrating psychological control alongside physical domination. Later revelations show Genosai himself was under Abraham's influence during these events.

Genosai's role shifts when Abraham fully manifests, possessing the original hero Lamune to become Black Lamuness. This transforms Genosai from primary antagonist to a figure seeking redemption. He participates alongside the heroes in a combined energy attack against Abraham's true form, resulting in his temporary petrification alongside Lamune, Milk, and the Arara princesses.

His legacy includes indirect influence through BQ, an entity appearing after Abraham's awakening to command Narcist Dandy and Pheromone Lip, maintaining the antagonistic structure he originally established.