Su Bai didn’t go to the mortuary. Not because he killed Liang. No one would know he had gone nuts unless Seven suddenly became extremely narrow-minded and told the others. But Seven seemed unlikely to do that.
Most importantly, as a member of that temporary team, he withdrew at the last minute while he should have followed them into the cave or at least tried to find help, although it would make no difference if he did.
Fatty and Gyatso were alive, that was awkward. If they died, things would be much easier between Su Bai and Seven, even if there were a few audiences they hadn’t met.
Su Bai ordered a room in a hotel. It was only one day from the deadline of MT 1. Su Bai thought it would be great if he could complete MT 1 peacefully and start MT 2. Compared to Fatty and Gyatso, or even Seven, he was the most recovered among them all.