Supplied to Seito's military, they were used by Namba to give Seito an advantage over Touto in the war between the two countries, being his preferred nation to inherit Japan.
A pair accompanied Evolt and a Strong and Flying Clone Smash during their attack on a Touto city. When Kamen Riders Build and Grease showed up, Evolt had them attack the two Riders, but they were fought off by Build with a shot from his RabbitRabbit Form's Fullbottle Buster, which destroyed one and propelled the other at Evolt, who destroyed with a single chop.
A squad of Hard Guardians were sent along with Nariaki Utsumi and the Washio brothers to kill Evolt after his alliance with Namba fell through. They were all easily destroyed by Evolt after he transformed into his Black Hole form.
Later, after killing Namba, Evolt took control of Namba Heavy Industries' Hard Guardian army and their invasion of Touto. An army of Hard Guardians was later seen being led by Kamen Rider Mad Rogue in an attack on Touto, but they were fought off and destroyed by Kamen Riders Cross-Z and Grease.