Yep, this part was in the novel too, MC got a short identity crisis because the dying girls that had just seen th gosts of her 3 comrades noticed the grim reaper and he thought of himself as one, that is pretty dumb as she seeing the ghosts confirmed she had simply crossed the treeshold like he did and was able to perceive him, it was to throw the MC in confusion with negative thoughts.
It was pretty bad as he knows there is a afterlife and a grim reaper that appears when someone is going to die, is interesting how even if is someone close to him he can't perceive Death if his own life is not involved.