Undercover in the Demon Sect: The Saintess and Senior Sister Have Both Turned Dark

My name is Lu Chen. I'm from Blue Star, and after transmigrating here, I became a disciple of the Qingyun Sect. I spent three years undercover in the Demonic Sect, and today, my mission is finally over. Before I left, the junior sister who brought me osmanthus cakes every day asked, "Senior Brother, are you going to stay here forever?" I didn't answer. The next day, she chased me three thousand li with half the Demonic Sect at her back. Oh, right. She's the Demonic Sect's Saintess. I only just found out. Fortunately, I still have my senior sister. Gentle and dependable, she cut the Saintess's chains with a single stroke of her sword and brought me home. I said, "My senior sister really is the best." Later, she replaced my windows with dark greenwood. After that, for some mysterious reason, my sect exit token stopped working. Then one day, in my senior sister's room, I found the sword tassel I'd lost as a child, my worn-out old clothes, and the notes I'd scribbled. Every last thing. My senior sister smiled. "Now that you know everything, I don't have to pretend anymore." So, is it too late to switch sides and join the demon race?