As shown in the true ending, Venom finds out about the truth sometime between his tenure in Diamond Dogs, the established Outer Heaven, and during Metal Gear’s Operation Intrude N313, the mission where Solid Snake kills Big Boss, now canonized as being Venom rather than the actual legendary soldier. Narratively, this retcon works exceptionally well in relation to how Big Boss supposedly dies in Metal Gear but resurfaces in Metal Gear 2: Solid Snake. The big Hideo Kojima twist for MGSV involves the meta, fourth wall breaking revelation that the players were essentially playing The Medic from Metal Gear Solid V: Ground Zeroes, a blank slate that is hypnotized into believing he is the actual Big Boss, when in reality, The Medic – now called Venom Snake – functions as the real Big Boss’ body double. There wasn’t anything hard in depicting a “hero fallen into demon” because, essentially, this never happens, while the opposite does, tenfold Big Boss – as much as I love the character – is still depicted and propped up as a hero. This is the hardest part, but not depicting villain, hero fallen into demon. We have to head off while the end of story is already fixed.