When monsters breach the boundaries between Hell and the human realm to claim tainted human spirits, a young boy named Tsutomu finds himself under attack. Fortunately, he is rescued by a trio from the Monster Patrol: Enma-kun, the offspring of Enma; Yukiko, a snow maiden; and Kapaeru. These individuals, tasked with apprehending rogue monsters, have ventured from the otherworldly Yokai Elementary School to maintain order amidst the chaos.