Lu Yanchen chose to tell the truth after consideration of his moral values and humanity. However, he felt a sense of guilt toward Shi Ze. Hence, he did not hesitate at all when the latter asked him out.
Right at River Hucheng, Lu Yanchen assured Shi Ze that he would have his grandpa make use of his connections so that the latter's father would have a reduced sentence and be let off earlier. But, what he did not know was that Shi Ze's father had already died in an accident in the jail a couple of days ago.
The reason why Shi Ze asked him out was for revenge! Shi Ze walked in front of Lu Yanchen, smiling and thanking him. However, his face changed almost immediately afterward, roaring at Lu Yanchen coldly and telling him to stop with his hypocrisy!
Right after that, he pushed Lu Yanchen into the river.
As Lu Yanchen struggled in the waters, Shi Ze shouted at him from up above, blaming him for everything.