Most likely this is just another version of the main characters life - they did the same thing with Here is My Exclusive Indulge 1 and 2. Same characters but they made different storyline versions.
I just watched Train to Busan today. Watched Peninsula too - not as good as Train to Busan. I still have AIB 2 to watch and looking forward to Sweet Hime 2 and Uncanny Counter 2.