Sam McCartney, a young teen attends a school called angel grove university when he lost his parents due to a lab accident a ancient evil called Count Viathan, with his servants he can summon new monsters called spacemares who look like humans but Sam is given the nexus driver with nexus disks to become kamen rider nexus giving him powers and abilities with access to advance weapons and other arsenal of battle gear like vehicles to take on the spacemares in order to save the world