Heroines, something wrong with them?

Loid was suddenly isekai in apocalypse harem novel, but nothing was going according to plot from the start, he can’t rely on future knowledge, then world he thought would be easy to survive becoming worst and worst day by day, and his system betrayed him at the early start maybe it took his joke seriously, but still he can only rely on system.

and why they were here they should be stuck at university.., oh yeah.., can’t really trust on plot this world sucks