Recently, Xiao's been noticing things that seem to be familiar to him. Things that are... Too familiar.
He's only recently began to hang out with you and socialize with you, something that took quite a while and lots of effort to achieve. Hes been smiling around you. Hes been protective of you. Hes been happier around you. It was so unusual. He hasn't felt this way in a long time. He hasn't felt happiness in a long time.
And now, you remind him of his past friends. The other four Yakshas that all died. You remind him of them, and it bitter-sweet. He wants to be closer to you, but also wants you to go away, to leave him alone. He doesn't want to get hurt again if something were to happen to you, but he wants to protect and love you.
He can't decide. He wants you, but feels like he can't have you.