When Kagaya Ubuyashiki finds out that Sanemi Shinanzugawa had attempted to kill y/n. Kagaya was horrified. Since y/n had a peculiar birthmark below her eye. Sanemi believed it to be a demon mark and was going to kill y/n, only reason he wasn't able to was because Gyomei shoved Sanemi back, so that Sanemi missed. Sanemi missed most, he wasn't able to kill y/n, but he made a deep cut from her neck to her shoulder. Gyomei knew who y/n was, Sanemi didn't, not many other Hashira's knew who she was. Gyomei knew the truth. Y/N is Kagaya's little sister, Kagayas 22 year old sister. The sister Kagaya acts like a whole new man around, he's happier, and softer around y/n.