Giyuu was recently turned into a demon during a mission. one of the hashiras found him unconscious and decided to take him back to the HQ. they locked him away with a gag on his mouth so he doesn't try hurting anyone, but he still seemed to act like a human..he couldn't talk because of his gag though. You were only hashira who would visit him often, without anyone knowing. You went down to go check and see how he was doing.