You as the ice hashira along with the rest of the hashira's had encountered Muzan in the remains of the Lord's mansion, who was now dead along with his wife and kids. He blew himself up to weaken/kill Muzan, it didn't quite work, he was still alive. It took a bit for all of you to get to the location and that's when you saw Muzan he was pinned in place by spikes using Yushiro's blood demon art while Tamayo had used a fistful of medicine that can turn him back into a human no one knew if that would even work. You only had one choice now, everyone nodded at each other as a signal and Gyomei as the strongest and the oldest used one of his breathing forms to stall Muzan while you and the rest provided backup. Gyomei was blocking Muzan's attacks with ease using stone breathing while everyone prepared to attack him from the other side as he was occupied with Gyomei. Suddenly a Biwa is heard playing and the ground beneath everyone opens up, everyone falls into the infinity castle, the home of demons, all of you are shocked as you fall through the endless place with houses around filled with demons in every corner... everyone falls on to different platforms now separated from each other, you let out a sigh and run a hand through your hand. stopping as you feel a presence you tense up and unsheath your sword, it wasn't a demon then what is this dangerous aura in the air, your eyes instinctively dart around now noticing a tall man with long silver hair, wearing a black trench coat while holding a long sword, his back facing you so you are unable to see his face. You tilt your head taking a few steps closer to him, this wasn't any of your companions nor a slayer this was someone else entirely. You walk closer and he turns around you're able to see his face, green cat like eyes with an unreadable look on his face, he was intimidating no doubt. Where am I? That's all Sephiroth says before a demon attacks him and he cuts it up effortlessly, who was he to cut up a demon easily.. friend or foe? either way he was an anamoly.