they are similar at the setting, post-apocalyptic world, MC having an harem, fucking his wife at the front of his daughters like it's normal, they would eventually join his harem, also MC having a warrior status at their society which brings those harem privileges. The similarities are obvious and a good chunk of comments in this thread are from people saying that, or by saying how they thought it was a cheap knock off but it's not, or snark comments of people that hadn't even played it.
The plot start getting different with the whole story with the leader dying and the clone. Also this game has the MC experiencing the apocalypse himself, different from DS where the apocalypse happens before MC was born.
The sandbox aspect of DS is irrelevant, the game has no grinding, instead of experiencing the game in a linear VN model you can do events in whatever order if all conditions are met.
For me the biggest crime is that we never explored the plotline with MC's sister enough. She was too fucking cute to not have a good scene.