Hi there! That's the intended end of that particular route of the game so there's no bug. Try playing through the game again making different decisions and you'll see different endings. Hint: You can check the gallery on the main menu for an overview of all the endings available.
But I see a YouTube video. A nekojishi gameplay. And the makes the same choices than me. But he hasn't this problem. And why is the game end in a cave? I wish my better ends for the next update. No ends in the middle of a game.
My best guess would be that they must have made some other choices to you as there's another ending that has a similar scene but continues on past that point. If you need any help you can always try and look up a guide for the game. Hope that helps!
Thank you for your suggestion, but I also got on the idea about 2 days late. Too bad is that there are so many sad endings and And some of the endings also let you get the feeling that the game is crashed or that the game is incomplete and unfinished. Overall, the game is really well done and has almost no improvement options. The only thing I would improve would be the endings not so fast and they don't mess you up like that. You have the feeling that the endings only goes a few minutes and the rest several hours.
Nevertheless, my respect goes to the game manufacturers and helpers. Keep it up.
Sorry for my english, but I come from Germanny and I am not so well in write English and speaking english. I hope my English is Okey and you can accept my English skills.