I genuinely think this is the most Sima Jiao has been at peace in his whole wretched life, and that's saying something. The way she brings him peace, letting him rest with her in his arms, happy and content in their little inner world.
It's so telling that he feels sleepy when he's with her. Not only does he trust her enough to let his guard down (a first in 500 years), but that her existence has taught him to love and appreciate the most mundane of leisures: having good night's sleep, eating a hearty meal, buying little nick nacks, playing little pranks, exploring, etc.
Sima Jiao, whose entire existence is nothing but pain, torture, and survival, someone so suicidal who has never known the pleasures of living, found someone who craves life. In Tingyan, he learns the meaning of life and finds a purpose for his existence beyond serving as mere flesh, blood, and bones for consumption. In fact, he is continually surprised that she doesn't want to use him or kill him. To her, his life is his own; not hers for the taking. In Tingyan, he not only finds unconditional love but also friendship, trust, compassion, and companionship. She is, to him who has been untethered from life for so long, a home to come to and rest his weary bones. And somehow that is everything. Brb sobbing! 😭😭😭😭