@cryum Yuan Chu is just pretending to be a viper to piss off Gu Qing Ke. Plus she knows they were being watched which is why she put on the act. There's no excuse for everyone else in the story however. Ye Chen Yuan especially.
It's getting desperately necessary that the boy is possessed by something, and that that's what's wrong with him ~.~; Because otherwise... Actually, regardless, boy needs an intervention, I think.