Tarou Kusakabe, the Mouse Knight, fights alongside his loyal animal companion Lance Lumiere. A childhood friend of Sorano Hanako, he dreams of becoming a chef, often crafting snacks for fellow knights. His Domain Control ability enables precise air manipulation within a defined space, allowing him to slice vegetables or ignite alcohol by agitating air molecules, stabilized by strategically placed pebbles.

His contractual wish activates when Hanako remains conscious during an attack, transferring her fatal wounds to himself—an unspoken act of love she recognizes in his final moments. During the clash with the ninth golem Boedromion, Tarou intercepts a lethal strike meant for Hanako, resulting in mutual impalement. Though his wish already guaranteed her survival, his physical sacrifice rallies the Beast Knights, who adopt black attire as a collective mourning emblem.

Hanako, haunted by his loss, later confronts Boedromion alone, channeling his legacy through an attack implicitly bearing his name. His death fractures the bond between their animal partners: Lance withdraws, while Kil Zonne lingers near Hanako despite her efforts to distance herself.

Etymologically, "Kusakabe" blends characters for "sun," "below," and "part," while "Tarou" derives from "thick" and "serene," reflecting his steadfast protection and composed demeanor. His relationships and background remain unaltered across all documented media adaptations.