The Yomi-Kugutsu are soldiers in red cloaks and full-body armor occasionally found patrolling locations of importance to General Munakata, and are ostensibly members of his Special Guard. They are very heavily armored and possess a degree of proficiency in combat, both with their weapons (swords and common guns) and with simple martial arts. Their main asset is their superhuman endurance, which allows them to easily shrug all but the most damaging attacks.
It is a group of several of these soldiers who abduct Kaya Daidouji and confront Raidou Kuzunoha the XIV, and returned constantly as elite bodyguards of Munakata's. Sadakichi, a Navy spy planted in Munakata's organization, eventually reveals what he's pieced together about the monstrous truth of the Yomi-Kugutsu - the entire squadron is a group of armored, soulless zombies, conditioned to obey the will of the controller. Munakata himself is often guarded by large groups of the monsters.
Large groups of Yomi-Kugutsu were used as the crew of the Soulless God Oumagatsu. When the main controller of the group, Sukuna-Hikona, was slain, most Yomi-Kugutsu were left without a commander and were presumably destroyed.
"A invincible soldier animated using the Hiruko. Developed in secret to form the military's Soulless Army. The emotional traumas characterizing the Red Capes has been removed using Specialized equipment."
—Gouma-Den Devil Chart
The Yomi-Kugutsu return in a Case File, as it is revealed a rogue battalion of the elite soldiers continued executing its orders, without realizing its commander was long dead; they were easily controlled by the rampaging god Okuninushi, who sought to complete Sukuna-Hikona's vision. The somewhat clueless group continued patrolling the remnants of the Army's Subterranean Shipbuilding Facility until destroyed by Raidou. Yomi-Kugutsu come in three summonable variants: Lvl. 17, Lvl. 24, and Lvl. 55.
Another battalion of the undead soldiers, stationed near Tsukigata Village, went rogue and deserted in a futile attempt of the zombies to return to their native village. Raidou found and finished them, granting them the rest they were unable to find elsewhere. Gouto-Douji commented on the unfortunates who had the bad luck of being drafted into the squadron and asked Raidou to honor the fallen soldiers by ensuring their safe burial.