The Nonhuman Side refers to the main storyline decision presented to the player regarding how the game will end in Radiata Stories. Jack is given a choice to "Follow Ridley" or "Meet Larks at the castle" during what is commonly referred to as the "split" that occurs roughly halfway through the game.
The remainder of the game takes place outside of Radiata City and involves the recruitment of nonhuman characters. Jack fights Aphelion the Silver Dragon to save Ridley, which this brings the era of the Golden Dragon and the destruction of all humanity. Jack and Ridley are then seen returning to an empty Radiata Castle together.