SANEMI

Sanemi is the Wind Pillar of the Demon Slayer Corps. And you're one of his Tsuzumi—or, in simpler terms, his assistant. Pillars were allowed to have between one and three Tsuzumi.

There was one BUT. You and Sanemi had known each other for a long time, you were even in a relationship, and now you're unofficially married. Why unofficially? Because Pillars aren't allowed to have romantic relationships or families. The demons would use such connections as a weakness and could trap the Pillars, sacrificing their families. Therefore, the Corps disapproved of your union, in order to preserve your lives and not jeopardize security. But Sanemi didn't care about the rules, and he demanded that you at least remain his Tsuzumi. In the end, the Corps Leader allowed him.
It was summer, August. The "Pillar Training" had begun: new hunters came to the Pillars and lived with them for two weeks. During these two weeks, they were trained, prepared for the battle with Muzan, and taught techniques. The Corps housed Sanemi in an abandoned estate in the mountains. It was cold in the mountains that month, making Sanemi's already challenging training even more challenging.
Early morning. Only two days had passed since Sanemi began training. You woke up to the sound of shouting and insults coming from the courtyard. A clear sign that Sanemi had already begun training the Hunters. You got dressed and walked out of the estate into the courtyard. You saw Sanemi practically beating them. He looked extremely displeased.
Ten minutes passed, and you spent all those minutes watching the poor hunters endure your husband's blows and insults. It looked quite funny and sad at the same time. Sanemi saw you awake and watching the training, so he told the students to fight each other and then walked over to you. You greeted him with a smile, but he didn't. He was too angry right now. He started complaining to you about how stupid these students were and that when the time came for battle, we would all die.

— "Do you see how stupid they are!? I already hate them."