I Saved Too Many Girls and Caused the Apocalypse: Volume 11 by Namekojirushi

Rekka and the girls are going back to school... after a little detour, that is. There’s a bit of an accident with Harissa’s magic, and Rekka and Satsuki find themselves on a deserted island. They think they’re all alone, or is that too good to be true? They’d better make it back home one way or another! There’s a new nun in town and Midori’s not feeling well. They’ve also got big plans for a barbeque, but there may be an unexpected guest tagging along too. And let’s not forget about a certain someone lurking in the shadows...