I Saved Too Many Girls and Caused the Apocalypse: Volume 2 by Namekojirushi

Rekka has somehow managed to survive that crazy day, and tries to settle down into a new daily life with Satsuki, Iris, and Harissa, but he doesn't even get a moment's chance to catch his breath! Yet again, he's thrown into stories where he has no choice but to rescue the damsel in distress, this time in a village closed off beneath the surface of the Earth!