"Z-zenitsu, help me, please!" Tanjiro murmurs, voice barely audible. Zenitsu's eyes widen. He runs over to check on Tanjiro, knowing fully well that he is in the enemy's territory. But this is a scary situation. Zenitsu is a coward, and a coward knows when to run. There's too many red flags, so why isn't he running?
The first red flag being that despite being pulled into this maze-like place no one is attacking him. No one, even though he's sure he senses some 2 to 3 demons. The second one being that Tanjiro, of all people, is kidnapped, and is trembling. Under normal circumstances he would have definitely fought back. But there aren't any wounds either.
Zenitsu goes to the tiny ball of Tanjiro. And the third, most unsettling red flag Zenitsu notices, and he really hope his ears are messing with him or something, is that Tanjiro sounds like a demon.
"Y-you're not Tanjiro," Zenitsu is sure.
"No- they- Muzan forcefully turned me!" Tanjiro shouts, tears forming in his eyes. Upon hearing that, Zenitsu hears a hint of that gentle sound he had heard when he first met Tanjiro. His hands which he had been unknowingly gripping on his sword begins loosening.
And Zenitsu, is slowly, but surely, letting himself believe this lie. He knows he is, but it's okay. No one ever thought that he mattered anyway, did they? Gramps is probably disappointed that he can't have a proper successor. Inosuke always shits on his existence. Nezuko doesn't even pay attention to him. And now Tanjiro is a demon. If he's going to go, at least it's Tanjiro that's taking him. And that's okay.
Tanjiro.. are you oka-" before he manages to finish his sentence, Tanjiro pushes him down. He goes in for a kiss, and aggressively so. Zenitsu's sure he's choking, bleeding(on the lips and tongue), crying, salivating but it feels like sweet release. Honestly, he's just happy he gets to see Tanjiro one last time before he dies. After all, Tanjiro had went missing for 3 whole days.
It's okay, it's okay, it's okay-
Suddenly there's a sharp pain in the middle of his forehead and Zenitsu looks up to find Tanjiro's finger digging into his head where the pain is. His widened eyes finally made contact with Tanjiro's.
"Meet our new uppermoon 6, Zenitsu," He hears Muzan, smiling victoriously.
He doesn't get the time to process this but he's already losing his mind, the transformation is already happening. His whole body is shaking. His eyes move back until only the whites are visible and he feels fangs and nails painfully growing.
What a painful process, the last of his humanity says.
"I hope I have done well, Lord Muzan. But may I know who that was?" Tanjiro voices, gently stroking the seemingly lifeless body.
Before Muzan could answer, the biwa is heard and soon so is Inosuke.
"Monitsu!! Kentaro!!! Monitsu!!! Kenta-" he turns towards Tanjiro and Zenitsu, shock soon turning into anger.
"Do I have to handle him too?" Tanjiro asks.
"No," Muzan replies. "We already have a hungry demon." Muzan points to Zenitsu, who is now awake once more, and is growling. He is indeed hungry, and there is one human in this space that can help him with that.