Ok so like, what's preventing someone from sweeping the game by killing everyone outside? Shinji can probably no-diff everyone that doesn't have a gun while unarmed.
No one is questioning that big man does have incentive to frame Yuuichi since he lost everyone's trust on day 2. Also this shit could've been prevented if Shiho just followed big man to the cave, see what he did to Yuuichi and save a looooot of trouble on who's the culprit.