What did I do wrong? I keep getting a bad ending in chapter 4 and have no clue what I did wrong, I just die in the tunnel.
This happens if, like other poster mentioned, you don't gain enough romance points with any of the ROs. IIRC you need something like 6+ points for that person to become option you can select as your rescuer.
This can be a result of either picking responses in interactions with them which don't match their preferences, dividing your attention between ROs and thus missing out on opportunities to increase your standing with one person, or a combination of those.