“Your phone number was the only one I knew off by heart.” 

「路呢，都是自己选的」

The resignation on Chusheng’s face says it all I think - Zhang Yunlong actually said in an interview that aside from all the comedic and fun parts to MRIAD, for Qiao Chusheng, MRIAD is actually quite a tragic and sad story for him.

When he says 落子无悔, a more accurate interpretation to this would be, since he has already made all the choices he has so far, there is no point in regretting what has been done and it makes me sad because this man has given his everything to Boss Bai, to Youning, and finally, to Lu Yao, up to this point. It’s not that he has no regrets I think, it’s more that it is futile to linger on them. All he can do is move forward, even if it makes him unhappy.

He doesn’t want to fight the war, he doesn’t want to kill anyone, but for Boss Bai and to protect both Youning and Lu Yao both of whom he loves, he will go wherever he’s told to go. He didn’t want to become Inspector - in the first episode, Lu Yao correctly points out that Chusheng’s not exactly qualified for the position, but Boss Bai installed him there (of course correctly, and QCS was made for the job), so he took the position. And how many cases has he done at Boss Bai’s behest, only to realize that he’s caught in a difficult position because he might not be able to go after a culprit or suspect (luckily, he has Lu Yao, but if he did not)?