A Tale of a Split Mind is a short story written by EnderEmerald46.
One day Amethyst is showing Apatite a game outside (the game is up to debate), however due to bad weather conditions the two get struck by lightning. When the two wake up, Apatite's purple eye is his natural green again while Amethyst's right eye is now orange, which makes Apatite realize (as well as seeing his gem un-glitched) that Obsidian is no longer in his body, leading to slight excitement by Apatite. When Amethyst asks what she should do about the fact she's glitched, Apatite explains that now that he's unglitched, he'll be able to research must better than he used to (Since he won't be distracted when Obsidian takes over), so he'll be able to fix it faster. He gives Amethyst a quick review of what the glitch does, and, thinking she now has Obsidian, Amethyst accepts her new persona. She then returns to the beach house, where Pearl asks what happened and Amethyst explains that she now has a split persona.
It is around here where Amethyst changes for the first time, switching into her new persona, Citrine, who is similar to Pearl (but the persona is male). The switch is rather brief, however it soon becomes more and more active, as well as Citrine gaining a dominance in Amethyst's appearance. It mainly freaks Steven out, and while Pearl says she likes the change, but secretly doesn't like it (which is revealed later). Meanwhile, Garnet finds Apatite, who realizes that even though he can research must faster, without Obsidian, it all becomes rather boring, and yearns for her to come back, if only so that he doesn't go crazy from boredom (or at least that's what he says XD).
Garnet then explains the situation to him (which may involve trying to hurt him, due to her thinking he did it on purpose), causing Apatite to realize he can keep the glitch in line better due to being the original host. The two then rush back to the beach house, where Amethyst is repeatedly switching between and fighting for control against Citrine, which is slowly becoming a losing battle. Apatite then manages to pounce on Amethyst again, seeing another bolt of lightning, knocking the two unconscious again. When the two wake up, they are back to normal, Amethyst being Amethyst and Apatite being glitched, and as Apatite leaves he's mostly relieved that Obsidian is back, ending the episode with a smile on his face.