Disclaimer: Demon Slayer: Kimetsu no Yaiba and all its scenes, characters, etc. based on it, including the soundtrack, etc. belong to their respective owners (Koyoharu Gotouge, etc.). Cover image by moritolili on Twitter. I'm merely writing this to entertain and I don't get any profit out of this.
Zenitsu's sword was rarely seen in combat. His attacks were way too fast. They only time anyone could catch a glimpse of his sword was when he took care of it, cleaning and polishing it. One day Nezuko saw Zenitsu cleaning his sword and was mesmerized by its golden shining.
She took a look at the weird dandelion, who was handling his weapon with all due care. It was clear that he loved his sword. No wonder it was so deadly if it was under such good maintenance.
Zenitsu heard Nezuko by the door and immediately gazed at her.
"Nezuko-chan! Did you come to see me? Please, come in! Don't be shy!"
Nezuko doubted for a moment but at the end decided to enter the room to admire the beautiful sword of the weird dandelion. It was white and yellow, with a golden bolt of lightning in the blade. She was staring at it intently and he noticed.
"Oh... So you wanted to see my sword..." Zenitsu was disappointed but still glad she liked his nichirin blade nonetheless. She had never shown interest in any other weapon, much less something that could be deadly to her. He felt proud of the fact that only his sword had caught her attention.
"It's beautiful, isn't? My favourite thing about it is the lightning. It makes it look so awesome! I just wish I was worthy enough of it..."
Nezuko noticed his tone had become sad and she felt bad. The weird dandelion always looked happy when she was near. She didn't want him to be gloomy. Also, what did he mean? The sword was golden and shone just like him. They were perfect for each other. She shook her head and pointed at the sword and then pointed at him and nodded vigorously.
Zenitsu felt tears coming to his eyes.
"Nezuko-chan... Are you saying... You think I'm good enough for this sword?"
"Mmmmm!" She nodded energetically again.
"NEZUKO-CHAN! YOU'RE SO KIND, NEZUKO-CHAAAN! I CAN'T WAIT TILL YOU'RE HUMAN AGAIN SO WE CAN GET MARRIED!" He was crying a river. Nezuko got a bit nervous and didn't know what to do, but then Zenitsu, noticing she was uneasy, took her hand and looked at her in the eyes with sincerity.
"Thank you so much, Nezuko-chan. This means the world to me."
Nezuko smiled behind her muzzle. She was glad her weird dandelion was happy again.