C1022 New Thoughts
Back when the plan failed, it wasn't because the Eldest Prince was sparing due to sibling affection, but because he secretly warned Murong Xue, giving her time to prepare. He's quite petty; since the Eldest Prince almost harmed Murong Xue, he feels the need to seek justice for her.
Qin Huai couldn't come up with a strategy right away, so he didn't linger. He quickly left
