Yu Yu Hakusho (1992)

S3E3 The Power of Taboo

Kaitou's sinister game turns into a perilous struggle as Hiei, Botan, and Kuwabara fall victim to the teen's strange regulations. However, Kurama steps up with a bold challenge: each letter of the alphabet will be declared off-limits. Anyone who dares to say a forbidden sound will incur a harsh punishment. With everything at stake, including his own soul, Kurama gears up for an intense mental duel against the cunning Kaitou.