This is the Solution for these Guys who are not able to get Achievements!
Just follow these steps
1. Deinstall the Game.
2. Close Steam completely (stop the Prozess!).
3. Delete these 2 Folders:
...\Steam\steamapps\common\one night, hot springs\onsengame-market\game\saves ...\AppData\Roaming\RenPy\onsengame-1517489131
4. Start Steam.
5. (Re-)Install the Game.
6. Play the Game.
7. Enjoy the Achievements!
Thanks to WhizZy for his great guide, all credit to his effort. you can also read the original guide from Steam Community. enjoy the game.