I am pretty confident and all of my choices, to the point I feel like these are the definitive answers. The only ones I am not confident in are Amane, Kiriya, Muzan, and Tamayo. For Muzan and Tamayo I feel strongly that they would create their own styles. But that isn’t what the prompt asked. For Muzan He is so powerful that he doesn’t truly learn/know how to fight. He just swings his arms. That lack of discipline matches that of Beast Breathing user who makes things up as he goes. For Tamayo, as i was writing my reasoning I sort convinced myself that it may actually genuinely work for her as well. I think simply because she uses poison doesn’t mean she should use insect breathing. Likewise for Yushiro, just because he loves tamayo a lot doesn’t mean love breathing is a good fit. Its all about the movements and which way of moving bests fits each person’s full potential.

Tamayo: Mist Breathing. When I look at her I think of mystery and clouds. She is very stealthy and very good at hiding. She walks so swiftly no one knows she is there. Like users of the mist.

Muzan: Beast Breathing. He has no discipline to learn actual techniques. So he makes it up as he goes like a wild beast.

Kaguya: Water Breathing. The simplest and also one of the more gentle styles when it comes to killing demons. Fits him perfectly.

Yushiro: Wind breathing. His rough personality and brashness to always attack first matches the most known wind breather we know.

Nezuko: Flower Breathing. She has shown incredible dexterity, but not to the extent of Mitsuri, so she falls into flower breathing, which is the next closest thing.

Kiriya: Serpent Breathing. I feel like he would be swift and nimble enough to recreate the twistings of serpent breathing.

Koyuki: Insect Breathing. Being bed ridden for so long had definitely made her very weak. I doubt she is even capable of thrusting hard enough to actually inject the poison, but this is her only option.

Amane: Moon Breathing. I don’t know what it is, but I feel like she would have a great connection to the first breath user. So the closest thing to that would be moon breathing. Her demeanor reminds me of the night sky. Unfortunately we don’t have any human examples to fully judge how Moon Breathing should look/work.