Ohh, I stand corrected, so at least he didn't abuse the synthesis system (unless the characters didn't earn their keep at all). Well, that explains why his home base had like 25k people in it, haha. Truly a small kingdom in its right.
The idea that the entire world literally had no more heroes is soul crushing as well, and he did the best he could. As it shows, you can pick almost anyone up and develop/upgrade/promote them if they show enough potential, but we all know how gacha geeks are obsessed with growth rates and not losing a single stat point.