Presented as a game to "discover oneself", the game revolves around the player wandering in a monochrome library-like world and being guided by a mysterious woman named Es.
The player wanders through an endless aisle where they click thought bubbles, which generally show quotes from literary classics and phrases related to the personality tests Es gives to the player, to collect EGO points. They can also buy books which allows the player to passively accumulate EGO points and "read" pages of said books to upgrade the books' accumulation rate.
The main story progresses when the player reaches an EGO point milestone.
Originally released on mobile devices in Japanese, the game eventually got an English release.
A version of the game for Nintendo Switch called ALTER EGO S is set to be released in 2020.
Not to be confused with the 1986 game of the same name or tropes pertaining to an alter ego, nor with a different game of the same name released for the PC and Wii. Nor with the app version of the Artificial Intelligence from Danganronpa: Trigger Happy Havoc.
This game provides examples of:
- Anti-Villain: Ego Rex can be interpreted this way. They'll repeatedly tell you to keep Es conforming to their rules and regularly calls her a failure. However, considering what happens when you set Es free, their actions are somewhat understandable. Besides, they never actually try to stop you from getting the other endings, and congratulate you if you reach the True Ending.
- But Thou Must!: At the final picture book, the game will force you into choosing one specific option of the three possible if you are in either of the bad ending routes.
- Cessation of Existence: Es does this to herself in the SUPER EGO ending.
- Cute and Psycho: Es during the ID ending.
- Deliberately Monochrome: the game is completely in black and white except for the butterflies.
- Featureless Protagonist: The protagonist's face is never shown.
- Freudian Trio: Ego Rex (the Super Ego), the Player (the Ego), and Es (the Id).
- Genius Bonus: Before being translated, Freud's original name for the Id was "Das Es".
- Great Big Library of Everything: Every literary classic seems to be available in Es' library.
- In-Series Nickname: The Facade is the name Es uses to refer to Ego Rex.
- Microtransactions: Players have the option to pay to boost EGO points, remove in-game-advertisements, and gain access bonus content.
- Multiple Endings: There's the ending of ID, in which Es goes mad and denies the world. There's the ending of SUPER EGO, in which Es denies herself and Ego Rex gains control. Finally, there's the ending of ALTER EGO, the true ending in which balance is found, Es is able to stay herself, and the credits roll
- My God, What Have I Done?: In the impulse ending, Es briefly regains her senses and asks the player to forgive her before she breaks the world.
- New Game+: You can start a new gameplay loop after reaching an ending. Starting a new loop resets all of your Books and bonuses gained from Es, but retains all of your achievement bonuses, allowing you to plow through early-game with your boosted EGO generation.
- Nightmare Sequence: The impulse and conformity endings may be this. In the true ending, Es mentions that she dreamed about denying her identity and vanishing from existence or giving in to impulse and becoming a Woobie, Destroyer of Worlds due to the Facade's pressure on her. She could also be Dreaming of Times Gone By.
- One-Letter Name: Es is alternatively known as "S".
- Pretty Butterflies: Glowing blue butterflies are a defining motif of the game.
- Player Personality Quiz: One of the main features of the game. Es from time to time gives the player personality tests.
- The Stoic: Es. She mentions that, even though her facial expression didn't change, she's happy to see you.
- Take a Third Option: The True Ending route, where Es realizes that she needn't choose between true impulse or true conformity and decides to continue searching for herself along with the player.
- When She Smiles: Es in the True Ending.
- Woobie, Destroyer of Worlds: In the Giving in to Impulse ending, poor Es goes mad and decides to destroy the library-like world of the game and go after the Facade.
- World of Mysteries: While the setting of the game looks like a library, the exact nature of the place has never been disclosed.