Yu Yu Hakusho (1992)

S3E21 Power Between the Teeth

While Itsuki delves deeper into the strange nature of Sensui, Koenma gets ready to deploy his ultimate weapon: his pacifier! This tool can generate a barrier strong enough to prevent demons from overrunning the Living World. Aware that Sensui's defeat is crucial to thwarting his malevolent scheme, Koenma realizes that failure would spell disaster for humanity as a whole.