Overlord Twitter Side Story is a non-canon side story written by Maruyama Kugane. The story was posted on Maruyama's Twitter account on September 26, 2015.
This side story from the author tells a different turn of events of the protagonist. Momonga enjoying the last hours of YGGDRASIL decides to spend his time outside of the Great Tomb of Nazarick. Upon exiting the tomb, he finds himself in a new world and meets an unexpected character.
When Momonga had enough of sitting idly by as YGGDRASIL is about to be permanently shut down for good, he makes the final decision to celebrate the end of the game in style. Reasonably so, he heads towards the surface teleporting through various rooms by using the Ring of Ainz Ooal Gown. He flies off to a small little island in the Grenbera Swamp and sets up 5000 fireworks to explode and burst into the sky. While blinded by the brilliant flash of light, Momonga notices that his surroundings have changed from a swamp to a ruin.
Unable to determine his situation and exact location, Momonga decides to patiently explore his new surrounding. To gather information stealthily, he turns himself invisible. At the same time, he also activated his passive ability to detect any Undead nearby. As a result, he could sense the presence of an undead close to his surroundings, causing him to hide momentarily before deciding to seek the target out. Momonga notices that the ruins are not made of reinforced concrete and believes he is somewhere in YGGDRASIL but determines it to not be the case as some of his spells behave differently unlike those from the game.
Using 'Distant Vision,' he sees it to be a mere zombie putting his mind at ease. He later detects another presence of an undead, this time heading away from him. Determined not to lose another source of information, Momonga tracks his newfound target. After catching up to the target, he realizes it to be just a little girl who is alone. He politely greets her and introduces himself as Suzuki Satoru. He asks where her parents are to which the girl responds by stating that they are gone, indicates she is an orphan. The girl later introduces herself as Keno Fasris Invern.
- Based on the non-canon side story, Momonga's arrival in the New World is implied to have taken place centuries earlier before the present day of the canon the Overlord series set off.
- Unlike the official story, in this non-canon side story, the Great Tomb of Nazarick didn't end up transporting to the New World other than one person being Momonga.
- A continuation of this side story was later written as the Overlord Bonus Volume and released in April 27, 2019.
- The side story was later converted as part of the prologue in the Bonus Volume.