I find that in the game, Morishige had never fully succumbed to ‘Insanity.’ In fact, I believe the only real reason he took pictures of the corpses was to keep his sanity on hold. It mentions that Morishige uses the tragedy to others to keep himself in a better position. All in all, Morishige’s my favorite, and he doesn’t deserve the hate he gets.
He was actually the one with less mental health even before he got in the H.H. Elementary School.
He went mad when he realized his dear Mayu was dead, and he toke pictures of her smashed body without knowing.
And right before knowing she was dead, tried to feel better about not having Mayu close to him…