OK...this is just stupid development. At this point the MC has all the tools he needs at his disposal to completely wipe out this camp and free his classmates.
Even without the skeletons , Kento alone could use his shadow walk ability to assassinate everyone in the camp.
heck even Reinheardt alone sent into the room the Princess is holding the meeting could easily paint the room red.
Heck he can just abduct the princess through the shadows start with the torture to have her tell him how to both release his classmates and return home, let's see how long she'll last being eaten alive by golbins and healed over and over again by the MC...
At this point the death of the bully, is as much the MC's fault as is the princess', he could have helped him at any time in a myriad ways by "spiriting him away",healing him or even just leaving some proper food next to his bed at night, but chose to bide his time instead.