Yes, in the "Demon Slayer: Kimetsu no Yaiba" series, Tanjiro Kamado becomes a demon temporarily. During his battle with the Upper Rank 3 Demon, Akaza, Tanjiro sustains severe injuries and is on the brink of death. In a desperate attempt to save him, his demon sister Nezuko offers her blood to him, and he drinks it.

As a result of consuming demon blood, Tanjiro undergoes a transformation and becomes a demon himself. However, due to his strong will and determination, he manages to retain his human consciousness and resist succumbing to his demon instincts.

While Tanjiro remains in a state of being a demon for a brief period, he continues to fight against demons and seeks a way to regain his humanity. His transformation becomes a significant turning point in the story, as he grapples with his newfound nature while striving to protect others and fulfill his mission as a Demon Slayer.