DECOY The Witch of the Blue

In this game, a prosperous civilization sinks into the sea, and the night never dawns. There is a feeling of apocalypse all over the world.
However, the characters who live there are by no means pessimistic, and spend their days lively, exploring ruins and doing their own jobs to earn a living, and it feels somewhat idyllic. You will land on an island in such a world, and explore the towns and ruins as you come into contact with mysterious fragments of the world.