You are bringing in a fair point, how DOES the imaginary freind in MCPN work? Like, normally having onea them can help with things like, talking with them making you calm down when scared, or they can tell you things you long forgot about, I guess gun control and combat tactics are also something they can tell you, but not shoot the gun themselves from another ghostly vessel.
I feel like it's just, the commotion and chaos of the battle causing agents to accidentally shoot eachother when you're not looking, and since the patient class has tonsa brain damage, they might also pull gun triggers without realsiing they do so; all those things go together into stuff randomly dying in ways a patient can only explain by "oh hey, my buddy helped me out again"; and you do play AS the patient in game, so you see things from their perspective also.
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Oh yeah, cool art by the way. The effects look nice.