A hero summoning.
To anyone aware of the term, it is a fairly straightforward deal.
Get summoned, learn that now you are a hero of some sort, defeat the Big Bad Evil Guy, and save the day. All of that for the sake of returning home and living a peaceful life.
If you are lucky, you might keep some of your abilities after going back, if not, you are at least left with an appreciation for the kind and peaceful world of today.
But what if, once everything is said and done, rather than going back home... You are sent to save yet another world? And then another? And then again, and again and again...
What if, after six entire lifetimes, when you grew accustomed to your new, bleak reality of ever-increasing hardship and challenges... You were to return home?
And could you really say you've returned... or was it your home world that summoned you back? And what's with the system making its appearance now, six lifetimes after it should appear?
***2 chapters/day