1x21 - Hell Teacher: Jigoku Sensei Nube

Mamoru is a healthy, soccer-loving fifth grader in Ms. Ritsuko's class. Or he was, until he falls ill after spotting a ghastly shadow dancing on a rooftop. Suspicious of his situation, Mamoru turns to Nube for help, which earns Ms. Ritsuko's ire. Though miffed, Mamoru would rather depend on the seemingly unreliable Nube. Ms. Ritsuko visits him in the hospital, only to witness a terrifying scene.