That one night (1)
*Flashback*
After the attack on Nana and Serena in the banquet by Tang Ning and Tang Feng, Shin didn't get a chance to introduce Huian as his girlfriend in front of Liang Xiao Dan and Liang Zou.
He had decided to tell them about her to let him off the hook to find a girlfriend finally, but the incident didn't let him. After that, Jinhai also stepped down from Liu Corps and was attacked by Moon Corps, so he thought of letting everything cool down before he would bring the subject again.
During that time, Huian and Shin frequently met together to know more about each other, not to expose their lie in front of them. They didn't want Liang Zou and Liang Xiao Dan to get suspicious of their relationship, so they used to meet up together and plan their conversations.
Even if it was all for the sake of their fake relationship, the process and meetings that happened during that time allowed them to bond with each other for real.