Responses
It's same universe, share characters and events, but it's not a side story.
There are two main series (webnovels) in this universe, each is planned to have six stories. Of those none is a spinoff or side story. "Kiss me liar" (Keith Pittman's story) belongs to the "Kiss me" series and "Kiss me if you can" (Chase Miller's story) to the "...if you can" series.
I just realized this was a side story to kiss me liar I'm such an idiot (T_T)