Do you choose just one option or did you try choosing a different answer? If so, I think it might be some sort of bug with the software itself, and if that's the case then unfortunately I can't do much until I can find a proper game engine to port it. I suggest saving before big choices and not clicking everywhere for now. Also do not save from the game window. Save in-game. It freezes and glitches if you try to save from the game window.
Yes please 'cause I'm confused. There's no serious option to choose in Death the Kid's route. There's only the serious word mentioned in Soul's route for one of the choices. It should be looking like this:
-Death the Kid: “Shall we go back?”
-”Accept his offer?”
Yes [toward Dtkromstart]
No [toward Dtkbadend]
Ahhh. I found the issue and I fixed it. Should be working now. You can redownload from the main page. Just a note, you can press and hold the space bar to go super fast on skipping the text. Also, you need to complete the good ending to unlock Death the Kid's final true ending route and then save the game after you reach it. Let me know if it works or not.