After all, I wonder if Waka and I are connected by a bond of fate

Waka married Ritsuki and lived happily for a year.
One day, Waka is lured by a mysterious voice at a shrine she visited for her cleaning event, and she
gets lost in a parallel world (another world) that is very similar to reality.

This is Saikado Island, one of Tokyo's remote islands that did not exist in the original world.
She meets Ritsuki in another world, and
Waka is relieved that Ritsuki and her are married in this world, but...