(on Chai)

Sanemi is the Wind Hashira and is the second strongest hashira as Giyuu is the water Hashira, the third strongest (in my opinion)

Giyuu went on a mission and met Muzan which he didn't know and he thought it was a normal demon so he tried to kill him but failed as Muzan wanted to turn Giyuu into a demon and so Muzan did, Giyuu passed out and was found by a demon slayer. He was brought back to the butterfly mansion was a treated until Giyuu wake up and felt different